First panel is the EFW spin fit (10.5 s) electric fieldin ~ dawn-dusk direction.This measurement is dominated by waves with amplitudes >32 mV/m ptp during during every storm as indicated by SYM H (third panel).

The second panel is the dawn-dusk electric field averaged over 10 minutes from both spacecraft (superposed). This is nomally the convection electric field- but it also includes contributions fromm injection events.

Notice the convection electric field is directed preferentially inthe positive dawn-dusk direction- the direction of sunward convection.

Notice also the convection electric field is often peaks at ~4 mV/m which is very comparable to the magnitude of the "solar wind electric field" (Vx sw x Bz sw). The solar windelectric field and the measured RBSP electric fields are largestduring the main phase of geomagnetic storms and smallerduring the recovery phase.

The bottom panel shows the solar wind flow pressure and Bmag. These typically are enhanced at the beginning of thestorm and models indicate thesubsolar magnetopause can move within ~8-9 Re durng the intial phases of the storm whenULF are strong. This may lead to effective radial transport outward and loss of particles throug magnetopause shadowing.

Towards the end of the storms, during periods of lower flow pressure, when the estimated position of the magnetopause is outwardmany storm have large wave electric fields. These are times when relativistic fluxes increase to and often above the pre-storm levels.

includes only EFW above 3.2 Re

SYM-H

Ey (10 min ave) – Convection- Efield

Ey (10.5s ave) Waves/ Injection Events

ECT REPT/MagEIS Electrons

May- June 2013 Storms

CBAAFTER

BEFORE

SYM-H

Ey (10 min ave) – Convection- Efield

Ey (10.5s ave) Waves/ Injection Events

ECT REPT/MagEIS Electrons

May- June 2013 Storms

Solar Wind Pressure

Summary

Almost all intervals of radiation belt increase or decrease are associated with large amplitude electric fields associated with waves 1-5 minutes

Waves at the beginning of storms are often associated with solar wind pressure increasesthat move the magnetopause close to the Earth.These periods are aasociated with decreases.

Wave occuring after the pressure enhancementsoften are associated with electron increases

• Before After Slides for Beomagnetic Storm of 5/25-5/26 2013.

A BAFTER

BEFORE

Time Lag between A and B

BEFORE

AFTER

BEFORE

AFTER

Summary:Abrupt enhancements or relativistic electrons on temporal scales of 1-5 minutes occur during the main and recover phase of geomagnetic storms.

We investigate these "prompt" changes during late May and early June of 2013 whenthe RBSP were "closely spaced" along their orbit with time lags between 20 minutesand 70 minutes. This allows a "before" and "after" snapshot of the relativistic particles and the electric and magnetic fields. In addition, it allows us to time motions of relativistic particle fronts and the driving magnetic and electric field changes.

In addition, the apogee is on the night-side. Inbound passes pass directly through the outer belts nearl local midnight. Outbound passess encounter the belts between duskand pre-midnight local time sectors

We focus on two kinds of changes... rapid temporal changes in the outer boundary of the position of the outer boundary of the outer belt and the motion of "discrete fronts" over the two spacecraft.

During these times the outer beltpasses over the two spacecraft over periods of 1-5 minutes when they are spatial separated by 0.4 to 1 Re typically in azimuth but alsoradially.

• The outer belts and these prompt changes occur in concert with large amplitude fluctuations in the electric fields in the dawnward direction of +/- 10 mV/m over (but ranging up to 40 mV/m) time scale of 1-5 minutes.

• Some of the largest electric fields are "unipolar" and directed dawnward. They dominate the azimuthal electric field component and should be especially effective in driving particles Earthward consistent with injection events. Their azimuthal correlation distance is ~1 Re.

For Ey ~ 10-40 mV/m fields over Δy ~1 Re~ E Δy = 100-400 kV. These vales are large compared to the steady-state large scale potential across the polar caps and flucutating over time scales comparable to drift periods of relativistic electrons. These fields are comparable or shorter than Alfen travel times along a field line and may never be completely communicated to the ionosphere in steady state.

• The relativistic fluxes enhancments near the outer boundary of the radiation belt and the leading edge of flux enhancements exterior are associated with slight (20 nT) magnetic cavities/ dcrements. These values are a fraction of the back ground B-fields of 100-400 nT.

• The are also associated with southward dipping of the magnetic field and/or poloidal fluctuations on time scales of 10-30 minutes

The motion of Relativistic Particle Boundaries/Fronts/Injections

East/ West and Inward and Outward. Injection Events.

Betatron Acceleration or Big Spikey Fields

Are the so-called cavities really cavities or are they temporal effects.

The role of the magnetic cavities.. The Role of Ring Current protons injection fronts in creating the Cavities.

Why do the relativistic electrons enhancments coincide with the cavities... the cavities are strongly dominated by the back ground fields.

Observation: The cavities move from one spacecraft to another in concert with relativistic fluxes.

Observations; They are associated with signifcant parallel Poynting flux towards the nearest hemisphere.

• The next two slides present Probe A and Probe B data over several orbits during which relativistic fluxes change between the two passes.

• Probe B leads Probe A by about 70 minutes.

• The Plot of Probe B has been shifted by 70 minutes so that time stationaryspatial structures are vertically aligned. So for example: the perigees of the spacecraft, the inner belts, the slot region are all aligned vertically.

Many structures near apogee and in the outer belts are not aligned. The relativistic electron fluxes appear to "move" or "grow" or "decrease".

All of these temporally varying structures are associated with strong electric fields (10-20 mV/m) over time scales of 20s to 20 minutes. Some resemble ULF waves. Others are unipolar and look like injection events.

You can see the temporal changes between the two spacecraft, by rapidly flipping back and forth between the next two "BEFORE" and "AFTER" slidesto create the illusion of a "movie". Use the "advance to next slide" and" go back to previous slide" ekys on your computer

SummaryA general pattern of relativistic evolution during a major storm is an initial decrease in MeV fluxes by several orders of magntiude during the early stages followed by increases in fluxesby several orders of magnitude during the peak and recover phases. Over the entire period of the storm, the net effect may be a net increase or decrease typically by an order of magntude for a moderate storm.

This study studies the storms during Spring of 2013 when the RBSP spacecaft on inbound passespassed through the radiation belts near local midnight. This is the first such study of the role of electric fields in accelerating energetic particles near local midnight since CRRES storms were not observed near midnight.

Here we establish from some of the first measurements of electric fields during storms near local midnight, that strong electric fields 10-40 mV/m) , either waves or implusive unipolar waves, or both are present during the intervals of flux decreases decreases and also during the increases.

relativistic electron enhancements associated with injection events that result in increases in flux by several orders of magnitude that alter the spatial structure of the radiation belts (broaden) There are also increases the flux at the peak of the outer belts by factors of 2-8.

• We have investigated most of the storms of Spring 2013 but focus on those storms for which the Van Allen Probes are "closely spaced" along their orbits, that is their time lag along theirnearly identical orbits is about one hour or less. At apogee this corresponds to about 1 Re in separation mostly along the azimuthal direction.

Slides for 6/07 to 6/08

Prob

e A

BEFORE

AFTER

Close-up View of Relativistic Flux Increase

• In the next slide, we look at a close up of one of the relativistic electron flux changes.

• We include a slide showing the Probe positions at this time.• The increase occurs at Probe A first followed by B several

minutes later.• This implies propagation of the flux enhancement towards

dusk at roughly 20-60 km/s• There is a similar time delay in associated perturbations in the

magnetic field.

• Most of the flux enhancement are almost simultaneous between the spacecraft with time delays of less than one to several minutes. We are still looking at them

A: 2.0 MeVB

A 3.6 MeV

B

A

B

The Storm of 5/25/2013• The next series of slides presents measurements from 5/25/2013. This is

another storm when the spacecraft were separated by about a 1 Re near apogee.

• You can see the initial decrease in REPT relativistic fluxes during the main phase and then a subsequent increase towards the end.

• Overall, from before the storm to after, the storm resulted in an increase in fluxes by almost an order of magnitude. This increase lasted until the next storm.

• The incidence of strong electric fields at the times of the decrease and increases are shown in the lower panel.

END

CBAAFTER

BEFORE

Geomagnetic Storm of 6/08

BEFORE

AFTER

Brought to you from the

"Cinematography Division" Space Plasma Physics Group University of Minnesota. and " Okey Dokey Productions"

AFTER

Prob

e A

BEFORE

file+ 2013_04_RBSP_ECT_LT.png

EFW E-Fields and ECT (REPT, MagEISElectron Fluxes during Geomagnetic Storms of April 2013

file : 2013-06-RBSP_ECT_LT_EFW_E_Field_month_gd.png ord pdf

EFW E-Fields and Relativistic Electron Fluxes from ECT (MagEIS and REPT) During the Geomagnetic Storms of June, 2013

EFW E-Fields and ECT Energetic Electrons (REPT/MagEIS) for Geomagnetic Storms of April, 2013

E-Field (duskward) 10.5 sec resolutionEy m

gse

AFTER

BEFORE

Close Encounters on the Storm of 6/01/2013

(20 minute time lag RBSP B leads.)

Observation of Intrusion of relativistic plasma

BEGIN of TIME LAG Dispalcement for 6/07/2013

END of TIME LAG DISPLACEMENT

Next Slide shows Probe B (blue) sees fluxes first then Probe A (red) Implies eastward motion of relativistic electron front- Drift direction of energetic electrons? Expansion of "plasma sheet"?

Orbit Plot for 6/07/2013 3:00 UT Encounter with Relativistic Electron Front

Next Slide shows Probe B (blue) sees fluxes first then Probe A (red) Implies eastward motion of relativistic electron front- Drift direction of energetic electrons? Expansion of "plasma sheet"?

Orbit Plot for 6/07/2013 3:00 UT Encounter with Relativistic Electron Front

file name : rbsp_A_B_REPT_timing_6_07_2013_3UT_0.25HR_vg.png/pdf

Relativistic Electron Front 6/07/2013 "Propagation" from B to A 2-4 minute delay

Outbound pass Probe A leads B by ~30 minutes.

Azimuthal separation; A East of B Probe A is in region of weaker B fieldB is in stronger

Azimuthal eastward/dusk transport of energetic particle front 30-70 km

Separation of spacecraft ~4,000km at 3:00UT (TBR)

Probe A leads outbound

Probe B trails

REPT 2-2.85 MeV electron flux

file name : rbsp_A_B_REPT_timing_6_07_2013_3UT_0.25HR_vg.png/pdf

Relativistic Electron Front 6/07/2013 "Propagation" from B to A 2-4 minute delay

Probe A leads outbound

Probe B trails A

REPT 2-2.85 MeV electron flux

GOES 13

file name : rbsp_A_B_REPT_timing_6_07_2013_3UT_0.25HR_vg.png/pdf

Relativistic Electron Front 6/07/2013 "Propagation" from B to A 2-4 minute delay

Outbound pass Probe A leads B by ~30 minutes.

Azimuthal separation; A East of B Probe A is in region of weaker B fieldB is in stronger

Azimuthal eastward/dusk transport of energetic particle front 30-70 km

Separation of spacecraft ~4,000km at 3:00UT (TBR)

Probe A leads outbound

Probe B trails

REPT 2-2.85 MeV electron flux

Postion of Probes (colored dots) during outer edge of discrete flux decrement at 4:00 UTon 6/07/2013. Probe A leads Probe B by about 30 minues or ~ 0.5 Re.

Probe A leading outbound..

END STOP