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. 2021 Jun 1;48(11):e2021GL092700. doi: 10.1029/2021GL092700

Prompt Response of the Dayside Magnetosphere to Discrete Structures Within the Sheath Region of a Coronal Mass Ejection

L W Blum 1,2,✉, A Koval 3,4, I G Richardson 3,5, L B Wilson 3, D Malaspina 1,2, A Greeley 3, A N Jaynes 6
PMCID: PMC8244059  PMID: 34219832

Abstract

A sequence of discrete solar wind structures within the sheath region of an interplanetary coronal mass ejection on November 6, 2015, caused a series of compressions and releases of the dayside magnetosphere. Each compression resulted in a brief adiabatic enhancement of ions (electrons) driving bursts of electromagnetic ion cyclotron (EMIC; whistler mode chorus) wave growth across the dayside magnetosphere. Fine‐structured rising tones were observed in the EMIC wave bursts, resulting in nonlinear scattering of relativistic electrons in the outer radiation belt. Multipoint observations allow us to study the spatial structure and evolution of these sheath structures as they propagate Earthward from L1 as well as the spatio‐temporal characteristics of the magnetospheric response. This event highlights the importance of fine‐scale solar wind structure, in particular within complex sheath regions, in driving dayside phenomena within the inner magnetosphere.

Keywords: dayside magnetosphere, EMIC waves, ICME sheath, radiation belts, solar wind

Key Points

  • A sequence of discrete structures within an interplanetary coronal mass ejection sheath are tracked via multipoint measurements

  • Each structure results in magnetospheric compression, adiabatic enhancement of ions and electrons, and cyclotron wave growth

  • This event highlights the importance of fine‐scale solar wind structure and sheath regions for driving dayside magnetospheric phenomena

1. Introduction

Solar wind structures act as critical drivers of magnetospheric dynamics, resulting in wave generation, magnetospheric reconfigurations, and geomagnetic storms. Magnetospheric responses, including particles and waves, to large‐scale structures such as interplanetary (IP) shocks, interplanetary coronal mass ejections (ICMEs), and co‐rotating interaction regions (CIRs) have been studied for decades. In particular, IP shocks have been shown to produce magnetosonic pulses that can propagate through the magnetosphere and resonate with MeV electrons, leading to particle acceleration and distinct drift echo signatures (e.g., Hudson et al., 2017; Kanekal et al., 2016; Li et al., 1993; Schiller et al., 2016). Shocks can also drive strong global ultralow frequency (ULF) waves (e.g., Hao et al., 2019; Kivelson & Southwood, 1985; Zhang et al., 2020), which can subsequently modulate magnetospheric particle populations as well as other active wave modes (e.g., Malaspina et al., 2015).

Pressure gradients in the ambient solar wind are another mechanism that can result in magnetospheric wave generation. Periodic density structures, often observed in the slow solar wind, can drive ULF wave activity in the magnetosphere at similar frequencies to those in the solar wind (Kepko et al., 2002; Kepko & Spence, 2003). These ULF waves can then modulate particles and other wave modes within the magnetosphere. Breneman et al. (2020) observed modulation of hiss waves throughout the plasmasphere induced by solar wind pressure variations and a “forced breathing” of the magnetosphere. These waves resulted in MeV electron precipitation, also showing ULF modulation. Liu et al. (2019) found quasi‐periodic electromagnetic ion cyclotron (EMIC) wave activity in the outer dayside magnetosphere as a result of ULF wave compressions, again driven by variation in the solar wind dynamic pressure. Finally, pressure pulses in the solar wind, whether associated with shocks, ICMEs, CIRs, or more moderate variations of ambient solar wind, can generate cyclotron wave growth in the magnetosphere. A number of studies have explored the occurrences of EMIC waves driven by solar wind pressure pulses, particularly in the outer dayside magnetosphere (e.g., Chen et al., 2019; Cho et al., 2016; Olson & Lee, 1983; Usanova et al., 2008, 2012).

ICME sheaths, the turbulent regions of compressed, heated plasma that form ahead of ICME ejecta, have gained attention for their effects on wave excitation and radiation belt dynamics. Recent studies have investigated the role of various regions of ICMEs in driving different radiation belt responses (Hietala et al., 2014; Kilpua, Fontaine, et al., 2019; Kilpua, Turner, et al., 2019; Turner et al., 2019). Kalliokoski et al. (2020) found that sheaths tended to produce enhanced EMIC and Pc5 ULF wave power as compared to ejecta and were associated with depletions in >1 MeV electron populations at L > 4. The enhanced density, temperature, and flow pressure typically found in sheath regions can result in a compressed magnetopause as well as increased ULF wave activity, leading to loss of energetic electrons both through the magnetopause as well as via precipitation into the atmosphere (Kilpua et al., 2017).

Here, we explore the effects of fine structure within an ICME sheath that impacted Earth’s magnetosphere on November 6, 2015. Utilizing multipoint observations in the upstream solar wind and dayside magnetosphere, we examine the Earthward propagation of a sequence of density and magnetic field structures in the sheath region. Each structure resulted in a compression of the dayside magnetosphere, adiabatic enhancement of ions and electrons, and subsequent bursts of EMIC wave activity. The sheath’s impact on both particles and waves throughout the inner magnetosphere is presented as well as the effects of these EMIC waves on energetic particles in the outer radiation belt. These observations suggest a close association between structures in the sheath, geomagnetic activity, and magnetospheric wave activity, to be explored further in this study.

2. Observations

To study the event on November 6, 2015, we combine measurements from a number of different observatories throughout the magnetosphere and upstream solar wind. Data sources include: solar wind parameters compiled from near‐Earth spacecraft as provided by the OMNI database (https://omniweb.gsfc.nasa.gov/html/HROdocum.html); vector magnetic field and thermal plasma measurements (where available) from the Advanced Composition Explorer (ACE) (Smith et al., 1998), Deep Space Climate Observatory (DSCOVR) (https://www.nesdis.noaa.gov/content/dscovr-deep-space-climate-observatory), Wind (Lepping et al., 1995; Lin et al., 1995) and Acceleration, Reconnection, Turbulence, and Electrodynamics of the Moon’s Interaction with the Sun (ARTEMIS) spacecraft (Angelopoulos, 2010; Auster et al., 2008; McFadden et al., 2008); high‐resolution magnetic field measurements from Geostationary Operational Environmental Satellite (GOES) 13 and 15 (Singer et al., 1996); survey mode vector magnetic field measurements from the Fluxgate Magnetometer (FGM) (Torbert et al., 2016) on Magnetospheric Multiscale (MMS) (Burch et al., 2016); fluxgate and search coil magnetometer measurements from the Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) (Kletzing et al., 2013) on the Van Allen Probes (refered to subsequently as RBSP A and B; Mauk et al., 2013) and ion and electron measurements from Radiation Belt Storm Probes Ion Compostion Experiment (RBSPICE; Mitchell et al., 2013), Helium Oxygen Proton and Electron (HOPE; Funsten et al., 2013), Magnetic Electron Ion Spectrometer (MagEIS; Blake et al. 2013), and Relativistic Electron‐Proton Telescope (REPT) instruments (Baker et al., 2013).

2.1. Solar Wind Structures

At 18:16 UT on November 6, 2015, an IP shock at the leading edge of the sheath region of an ICME impacted the magnetosphere, followed by a geomagnetic storm early on November 7. Figure 1 shows the (1a) interplanetary magnetic field (IMF) B total, (1b) IMF B z, (1c) solar wind flow speed, (1d) proton density, (1e) temperature, (1f) dynamic pressure, from the OMNI data set in which parameters have been shifted to the nose of the bow shock, and finally (1g) Sym‐H, a measure of the disturbance of midlatitude geomagnetic field, similar to the Dst index, often used to identify geomagnetic storms. The sheath‐ejecta boundary is indicated by the cyan line at 06:45 UT on November 7, the ejecta having the enhanced, slowly rotating, flux‐rope‐like magnetic field characteristic of a “magnetic cloud” (Klein & Burlaga, 1982). The shock at the leading edge of the sheath, marked by the magenta line, is associated with abrupt increases in the magnetic field strength, flow speed, density, and temperature. The sheath properties are consistent with those typically measured in such regions, namely higher densities and plasma beta, as well as frequent discontinuities presumably due to the accumulation of plasma and magnetic field from different sources as the ICME propagates through the solar wind (e.g., Kilpua et al., 2017). Roughly six distinct sudden Sym‐H increases (marked by the shaded orange regions in 1n) occurred between the initial positive excursion associated with storm sudden commencement and the main phase of the geomagnetic storm. Each was associated with changes in solar wind parameters—typically (1h) decrease in B total, (1i) a turning of IMF B z, and (1k) increase in density. The impact of these six features on magnetospheric dynamics will be explored in subsequent sections.

Figure 1.

Figure 1

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Solar wind properties, as provided by the OMNI database and propagated to the nose of the bow shock, and the Sym‐H index. (a–g) Measurements from November 6 to November 9, 2016, while (h–n) focus in from 16:00 to 22:00 UT on November 6. The magenta line at 18:16 UT marks the time of shock arrival, cyan line at 06:45 UT the boundary between ICME sheath and ejecta, and shaded orange regions on the right panels mark six positive Sym‐H excursions to be investigated further in this study.

Figures 2a–2d present the three‐component magnetic field in Geocentric Solar Ecliptic (GSE) coordinates as measured by L1 spacecraft and ARTEMIS ThC, with spacecraft locations illustrated in Figure 2e. ACE, DSCOVR, and Wind are closely aligned in x_GSE and span ∼150 Earth radii (R E) in y_GSE. Following the initial shock, which arrived first at ACE, clear magnetic field discontinuities showing very similar fine‐scale structure propagated past all four spacecraft, with the first three structures (the first being the shock) passing ACE at 17:35, 17:55, and 18:25 UT, and reaching ARTEMIS around 18:17, 18:39, and 19:01 UT. Shock parameters at Wind are estimated to be n = [−0.937, −0.348, −0.030] GSE, V shock = 578.4 km/s, Theta_B n = 47°, and Mf = 1.9 using a least‐squares fit of the full set of Rankine‐Hugoniot conservation equations to the magnetic field and thermal plasma measurements (e.g., Koval & Szabo, 2008, 2010; Szabo, 1994). Based on estimates of the shock normal and propagation speed at Wind, the intersection time at the bow shock should be ∼18:15:38—53 UTC and intersection point at [12.11, 10.03, 0.79] R E GSE. The shock arrival time in the OMNI data is in good agreement with this estimate as well as with the arrival time observed by ARTEMIS at 18:17 UT. A tangential discontinuity (TD) formed following the shock (∼4 min after at Wind and 6 min after at ARTEMIS). This has Theta_Bn almost 90° on both sides, propagating with the flow and in pressure balance on both sides (n = [−0.812, −0.421, −0.404] GSE, V TD = 483.5 km/s).

Figure 2.

Figure 2

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(a–d) Vector magnetic field measurements from ACE, DSCOVR, Wind, and ARTEMIS in the upstream solar wind. (e) Spacecraft locations in GSE coordinates at 18 UT on November 6. (f and h) B total and B z as well as (g and i) ion density at Wind and ARTEMIS, respectively. (j) Sym‐H, with vertical dashed lines marking the peaks of the six positive excursions.

Figures 2f–2i present B total, B z, and ion density n at Wind and ARTEMIS, the spacecraft for which thermal plasma measurements are available, as well as (Figure 2j) Sym‐H for timing comparison. The first three structures are once again clearly distinguishable, with distinct density enhancements corresponding to changes in B z and small depletions in B total. The first structure is bounded by the shock and TD and the second and third structures are each bounded by a pair of TDs with n = [−0.858, −0.363, −0.364] GSE, V TD = 512.4 km/s and n = [−0.834, −0.419, −0.360] GSE, V TD = 509.8 km/s for the second structure and n = [−0.832, −0.519, −0.196] GSE, V TD = 529.9 km/s and n = [−0.681, 0.049, −0.731] GSE, V TD = 441.6 km/s for the third structure. The double‐peak of the third Sym‐H excursion is mirrored in the B z profile at Wind (Figure 4f). Structures 4–6 are less easily distinguished in the density measurements but are still associated with discrete B z discontinuities and nonetheless produce clear positive Sym‐H signatures of similar magnitude to structures 1–3. This difference between the properties and magnitude of the structures observed at Wind and ARTEMIS as compared to the response of the magnetosphere could be due to propagation effects and structure evolution over time and space, or to a different combination of variables resulting in similar dynamic pressure and compression of the magnetopause.

Figure 4.

Figure 4

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Plasma and wave measurements from RBSP A. (a and f) Magnetic field spectrograms of EMIC and whistler‐mode waves, respectively, with white lines indicating the local H+, He+, O+ ion and 0.5, 0.1× electron cyclotron frequencies. (b and c) Proton and (g and h) electron energy spectra spanning eV–100s keV energies. (d and e) Proton and (i and j) electron pitch angle distributions taken at two example energies ∼20 and ∼200 keV, showing 90° peaked distributions during the compressions, as marked by the magenta arrows.

2.2. Magnetospheric Response

From 18:20 to 20:20 UT on November 6, a sequence of magnetic field compressions and bursts of EMIC wave activity were observed by multiple spacecraft on the dayside magnetosphere in response to the solar wind structures investigated in Section 2.1. Figure 3 shows (3a–c) the detrended magnetic field at GOES 13 and 15, RBSP A and B, and MMS 1, respectively, (3d–f) magnetic field spectrograms from RBSP A, B, and MMS 1, as well as (3g) the locations of these spacecraft during this time. A train of magnetic field disturbances were observed at all five spacecraft, with each corresponding to the impact of a sheath structure and positive Sym‐H signature from the previous section. The proximity of the spacecraft to the subsolar point influenced the compression signature each observed—for example, GOES 15 observed larger compressions than GOES 13 around 20 UT, while the disturbance at 18:20 UT was of similar magnitude or slightly larger at GOES 13. These signatures are consistent with the location of the shock impact at the magnetopause, just downward of the subsolar point, as estimated in Section 2.1. Coincident with these magnetic field compressions, simultaneous bursts of EMIC waves were observed by the RBSP and MMS spacecraft. GOES magnetic field sampling of 0.512 samples/s is unable to resolve these ∼1–2 Hz waves. Again, the wave signatures vary depending on spacecraft location, with the more dusk‐ward spacecraft (e.g., RBSP B and MMS) primarily observing the first three wave bursts, while RBSP A, closer to noon, saw additional bursts later in the period. Each compression was brief, lasting only a few minutes, and resulted in a correspondingly short burst of wave activity, turning on and off near‐simultaneously across the spacecraft spanning multiple R E across the dayside magnetosphere. During the first two wave bursts, the spacecraft spanned radial distances of ∼4.5–7 R E and 11:30–15:30 MLT, and by the fifth burst at 20:00 UT, which was primarily observed by RBSP A only, the spacecraft spanned 4.4–5.7 R E radially and more dusk‐side local times from 13 to 17 MLT.

Figure 3.

Figure 3

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(a–c) Detrended magnetic field measurements at GOES 13 and 15, RBSP A and B, and MMS 1, respectively. (d–f) Magnetic field spectrograms showing bursts of EMIC wave activity at RBSP A, B, and MMS 1. White lines indicate the local H+, He+, and O+ cyclotron frequencies. (g) The location of these five spacecraft from 18:00 to 20:00 UT, with filled circles indicating the location at 20:00 UT.

In addition to the geomagnetic field and waves, magnetospheric particles responded to the impact of the sheath structures. Figure 4 shows the wave and particle observations at RBSP A (similar electron and ion signatures are observed at RBSP B, MMS, and GOES, not shown). Panels (4b) and (4c) show proton energy spectrograms from the RBSPICE and HOPE instruments, respectively, collectively spanning energies from eV through 100s keV. Adiabatic enhancements across a wide range of energies were observed at each of the six wave bursts, with particle fluxes increasing during magnetic field compressions and relaxing to previous levels as the magnetic field returned to baseline. Pitch angle distributions at two example proton energies, (4d) ∼20 keV and (4e) ∼200 keV, reveal that the flux enhancements during the magnetospheric compressions were peaked at 90° across a large range of energies, consistent with adiabatic enhancement as well as with anisotropic conditions leading to cyclotron wave growth (T perpendicular > T parallel) (e.g., Cornwall, 1965; Gary, 1993). Xue et al. (2021) showed that these ion distributions provided sufficient free energy to produce the observed EMIC wave spectrum, based on linear theory. Figures 4f–4j show a similar scenario occurring in the eV–100s keV electron population and the resulting whistler‐mode chorus waves generated by these anisotropic electron distributions. Dayside compressions, driven by enhanced solar wind dynamic pressure, have long been studied as a source of both EMIC and whistler‐mode waves (e.g., McCollough et al., 2012; Tsurutani & Smith, 1977; Usanova et al. 2012). Compression of the magnetic field leads to betatron acceleration of locally trapped ions and electrons, generating anisotropic distributions that can provide the free energy for cyclotron wave growth (e.g., Anderson & Hamilton, 1993; Kennel & Petschek, 1966). We note that in this event the durations of the compressions and subsequent releases, corresponding to the sharp turning on and off of waves, were much shorter (<a few minutes) than most previous observations of compression‐driven waves, which are more often 10s of minutes to hours (Cho et al., 2016; Engebretson et al., 2015; Usanova et al., 2008).

Finally, we examine the effects of these brief but intense waves on higher‐energy MeV radiation belt electrons. During this event the impact of the initial IP shock, sheath‐region fine structure, resultant electromagnetic waves, and larger‐scale geomagnetic storm all combined to act upon relativistic electrons, making it challenging to disentangle the various effects of these different processes. However, we can examine the local response of MeV electron pitch angle distributions in coordination with high‐resolution wave measurements. Figure 5a shows the pitch angle distribution of 2.1 MeV electrons as measured by REPT on RBSP A during a 4‐h period around the time of interest, with Figure 5b showing a slice through the particle distribution at 90°. Both the adiabatic response of MeV electrons (e.g., at 18:20, 18:40 UT), as well as drift echoes due to the initial shock (e.g., at 18:30 UT) can be observed. To focus on the wave effects rather than those of the shock and geomagnetic storm, Figure 5c shows the pitch angle distribution during the second EMIC wave burst around 18:40 UT. Rising tone emissions are visible within this wave burst (Figure 5d), as have been observed previously during intense EMIC wave events (e.g., Grison et al., 2016; Nakamura et al., 2014; Pickett et al., 2010). Figure 5e shows a slice through both the wave power spectral density (green), taken at ∼1.6 Hz near the peak amplitude of the first rising tone, as well as through the 2.1 MeV pitch angle distribution at off‐90° (gray), taken at ∼58° here as fluxes drop off steeply at lower pitch angles and REPT does not measure pitch angles below 37° during this period, due to the configuration of the background magnetic field vector relative to instrument field‐of‐view. Faint enhancements of MeV particles at these lower pitch angles are observed, coinciding with the first two EMIC wave rising tones (Figure 5e). These can also be seen at 1.8 and 2.6/3.4 MeV (not shown), but the signal as measured by REPT gets very weak at energies beyond this. Similar signatures were observed by Zhu et al. (2020) and shown to be a result of nonlinear interaction between rising tone EMIC waves and MeV electrons, which can scatter particles toward the loss cone via phase trapping. Kurita et al. (2018) also observed scattering of lower pitch angle MeV electrons in association with EMIC wave activity. This event suggests that while short‐lived, these structured EMIC wave bursts can have rapid nonlinear scattering effects on energetic electrons, as demonstrated theoretically by Omura and Zhao (2012).

Figure 5.

Figure 5

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(a) Pitch angle distributions of 2.1 MeV electrons from 18:00 to 22:00 UT, as measured by REPT on RBSP A and (b) a slice through the distribution at 90°. (c–e) A zoom in on a ∼13‐min period during the second compression, showing (c) 2.1 MeV electron pitch angle distributions and (d) structured EMIC waves, with (e) electron enhancements toward lower pitch angles coincident with the first two EMIC rising tones.

3. Discussion and Summary

On November 6, 2015, a sequence of structures in the sheath region of an ICME impacted the magnetosphere, each causing distinct responses in magnetospheric particles and waves. Multipoint observations allow us to track the propagation of these structures through the solar wind as well as their effects across the dayside inner magnetosphere. Sheath regions are generally associated with enhanced density and variable magnetic fields but in this event the near‐shock sheath was made up of discrete density structures and magnetic field discontinuities that contributed to the almost periodic sequence of six magnetospheric compressions. The first three structures all seem to be of similar origin, bounded by tangential discontinuities, while the latter three are less clearly distinguished in the density measurements but still associated with distinct magnetic field discontinuities. While the cause of these structures is unknown and a topic for future investigations, their impacts on the magnetosphere are explored here. Each structure caused an abrupt compression and release of the dayside magnetosphere, strongest near the location of shock impact. Adiabatic enhancements of ions and electrons were produced in response, with profiles following the magnetic field compression profiles. These anisotropic plasma distributions resulted in near‐instantaneous turning on and off of EMIC and chorus waves. Such compression‐driven EMIC waves have been observed in a number of past studies. Fuselier et al. (2004) observed transient detached proton aurora across the dayside in response to IP shocks and attributed these to ion scattering by EMIC waves. One such event mapped to a region from 11 to 15 MLT and 5 to 8 R E, similar to the spatial extent observed in this event, and the authors found that shock impact angle related to whether aurora (and EMIC waves) were generated on the dusk or dawn side. Utilizing multipoint measurements, Engebretson et al. (2015, 2018) found EMIC waves spanning the entire dayside magnetosphere in response to sharp solar wind dynamic pressure enhancements and Blum et al. (2017) found wave extents to be more often larger on the dayside than nightside. The observations here are consistent with these studies and suggest dayside EMIC waves driven by solar wind compressions often span large spatial extents (∼3–4 R E and hours MLT) and have durations directly driven by variations in solar wind dynamic pressure.

While short‐lived, the EMIC waves observed on November 6 were of large amplitude and contained rising tones, which can result in nonlinear scattering of radiation belt electrons. A number of recent studies have investigated the role of ICME sheaths in driving different radiation belt responses (e.g., Kilpua, Fontaine, et al., 2019; Kilpua, Turner, et al., 2019; Turner et al., 2019). In superposed epoch studies, Hietala et al. (2014) and Kalliokoski et al. (2020) found enhanced magnetospheric wave power as well as depletions in MeV electron populations during sheath regions, and Kilpua, Turner, et al. (2019) found near‐shock sheath regions to be the most geoeffective. What superposed epoch studies do not reveal is the high amount of complexity and localized discontinuities within sheaths that may be a driver of wave and plasma variability. This study demonstrates that discrete structures within sheaths can produce distinct magnetospheric responses in both particles and waves and should be considered when exploring the response of the radiation belts to ICMEs. This event highlights the importance of fine‐scale solar wind structure and complex sheath regions in driving dayside magnetospheric phenomena not just close to the magnetopause but deep within the inner magnetosphere, generating particle and wave signatures spanning large spatial regions with temporal durations dictated by the solar wind driver.

Acknowledgments

The authors acknowledge the many scientists and engineers of the numerous missions whose data have been utilized in this study—including ACE, Wind, DSCOVR, ARTEMIS, GOES, MMS, and Van Allen Probe teams. L. W. Blum’s contributions were supported by the NASA Heliophysics Guest Investigator Program, Award #80NSSC21K0087 and L. B. Wilson’s by Wind MO&DA funds. The authors acknowledge the International Space Sciences Institute (ISSI) and the participants in a 2020 ISSI workshop in Bern on “Radiation belt physics from top to bottom.”

Blum, L. W. , Koval, A. , Richardson, I. G. , Wilson, L. B. , Malaspina, D. , Greeley, A. , & Jaynes, A. N. (2021). Prompt response of the dayside magnetosphere to discrete structures within the sheath region of a coronal mass ejection. Geophysical Research Letters, 48, e2021GL092700. 10.1029/2021GL092700

Data Availability Statement

All measurements utilized in this study can be found at the following websites: https://satdat.ngdc.noaa.gov/sem/goes/data/science/mag/ for GOES 13 and 15 magnetometer data and https://cdaweb.gsfc.nasa.gov/index.html/ for all else, by selecting the following spacecraft instruments and data products: ACE_MFI; ARTEMIS THC_FGM and ESA; DSCOVR_MAG; MMS1_FGM; Van Allen Probes_HOPE, MAGEIS, REPT, RBSPICE and MAGNETOMETER; Wind_MFI and 3DP; and OMNI_1MIN.

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Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Data Availability Statement

All measurements utilized in this study can be found at the following websites: https://satdat.ngdc.noaa.gov/sem/goes/data/science/mag/ for GOES 13 and 15 magnetometer data and https://cdaweb.gsfc.nasa.gov/index.html/ for all else, by selecting the following spacecraft instruments and data products: ACE_MFI; ARTEMIS THC_FGM and ESA; DSCOVR_MAG; MMS1_FGM; Van Allen Probes_HOPE, MAGEIS, REPT, RBSPICE and MAGNETOMETER; Wind_MFI and 3DP; and OMNI_1MIN.

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