Flare Irradiance Studies with the
EUV Variability Experiment on
SDO
R. A. Hock, F. G. Eparvier, T. N. Woods, A. R. Jones,
University of Colorado at Boulder
L. Didkovsky
University of Southern California
B. J. Thompson
NASA Goddard Space Flight Center
All about EVE
PI: Tom Woods, Laboratory for
Atmospheric and Space Physics,
University of Colorado, Boulder CO
SCIENCE THEMES:
1. Specify the solar EUV spectral irradiance and its variability on
multiple time scales
2. Advance current understanding of how and why the solar EUV
spectral irradiance varies
3. Improve the capability to predict the EUV spectral irradiance
variability
4. Understand the response of the geospace environment to
variations in the solar EUV spectral irradiance and the impact on
human endeavors
ILWS-2011 Workshop "Towards the Next Solar Maximum"
30 August 2011
Beijing, China
All about EVE
• Multiple EUV Grating Spectrograph (MEGS)

At 0.1 nm resolution

MEGS-A: 5-36 nm

MEGS-B: 35-105 nm

At 1 nm resolution

MEGS-SAM: 0-7 nm

At 10 nm resolution

MEGS-Photometers: @ 122 nm

Ly-a Proxy for other H I emissions at 80-102 nm and He I emissions
at 45-58 nm
• EUV Spectrophotometer (ESP)

At 4 nm resolution

17.5, 25.6, 30.4, 36 nm

At 7 nm resolution

0.1 - 7 nm (zeroth order)
• Solar Aspect Monitor (SAM)

.1 - 7 nm image
ILWS-2011 Workshop "Towards the Next Solar Maximum"
30 August 2011
Beijing, China
All about EVE
First light EVE spectrum with AIA & ESP bandpasses. EVE
measures the spectral EUV irradiance from 5-105 nm with 0.1 nm
spectral resolution a 10-second time cadence.
ILWS-2011 Workshop "Towards the Next Solar Maximum"
30 August 2011
Beijing, China
Temperature Coverage of
EVE
Peak formation temperature from CHIANTI vs. wavelength
for bright lines in a EVE spectrum (quiet Sun)
ILWS-2011 Workshop "Towards the Next Solar Maximum"
30 August 2011
Beijing, China
Active Region Evolution
5%
3%
Sub-daily variations in EUV lines are associated with
AR evolution and small flares
ILWS-2011 Workshop "Towards the Next Solar Maximum"
30 August 2011
Beijing, China
Solar Activity during Year 1
Levels of solar activity during the first year of SDO
observations
ILWS-2011 Workshop "Towards the Next Solar Maximum"
30 August 2011
Beijing, China
Space Weather & Flare
Location
Space Weather products are available from
http://lasp.colorado.edu/eve/data_access/
ILWS-2011 Workshop "Towards the Next Solar Maximum"
30 August 2011
Beijing, China
...not just flares anymore
2048 pixels
EVE is proving to be a remarkable
Future work will focus on moving from
qualitative study of the EUV irradiance
variability to quantitative study
ILWS-2011 Workshop "Towards the Next Solar Maximum"
30 August 2011
Beijing, China
1024 pixels
instrument for understanding the global
nature of EUV irradiance variability
Coronal Dimmings
Coronal dimming seen in both AIA 171 channel and EVE 17.1
nm line
ILWS-2011 Workshop "Towards the Next Solar Maximum"
30 August 2011
Beijing, China
Radiative Output of Solar
Flares
Four M1.0 flares have significantly different light curves in the
EUV. EVE allows us to quantify how the corona cools after a
flare.
ILWS-2011 Workshop "Towards the Next Solar Maximum"
30 August 2011
Beijing, China
Flare Classification
ILWS-2011 Workshop "Towards the Next Solar Maximum"
30 August 2011
Beijing, China
Compact Flares
C2.2 on 25 October 2010
Non-eruptive
Cohesive group of loops brighten concurrently
ILWS-2011 Workshop "Towards the Next Solar Maximum"
30 August 2011
Beijing, China
Localized Eruptive Flares
C4.6 on 12 November 2010
Localized brightening associated with EUV surges
Occurs at the edge of an AR at the footpoint of a loop that
connects to a different part of the AR or to another AR entirely.
Possibly the Skylab point flares previously categorized with
compact flares
ILWS-2011 Workshop "Towards the Next Solar Maximum"
30 August 2011
Beijing, China
Arcade Flares
C2.3 on 14 December 2010
Long(ish) duration events with EUV emission lasting hours
Generally associated with filament eruptions & coronal dimmings
Arcade of post-flare loops in corona and 2-ribbon footpoints in
chromosphere
ILWS-2011 Workshop "Towards the Next Solar Maximum"
30 August 2011
Beijing, China
Late Phase Flares
C8.8 on 5 May 2010
 Two spatially-distinct but related enhancements in 2-3 MK emission
tens of minutes to hours apart
 Previously observed but EVE has shown that these flares have a
strong and unique irradiance signature that can account for up to
40-80% of the energy radiated in the EUV
ILWS-2011 Workshop "Towards the Next Solar Maximum"
30 August 2011
Beijing, China
Example of a Late Phase
Flare
Comparison of AIA and EVE lightcurves & a cartoon of
the evolution of the 5 May 2010 C8.8 flare
ILWS-2011 Workshop "Towards the Next Solar Maximum"
30 August 2011
Beijing, China
Distribution of Flare Types
ILWS-2011 Workshop "Towards the Next Solar Maximum"
30 August 2011
Beijing, China
Distribution of Flare Types
ILWS-2011 Workshop "Towards the Next Solar Maximum"
30 August 2011
Beijing, China
Future Work
Continue to update the flare catalog including
Adding ~150 flares from March 2011
Adding association with CMEs
Validating impulsive phase using RHESSI data
Validating extracted parameters from EVE data
Start to associate flare parameters with physical
quantities:
Loop length
Arcade length
Magnetic field strength
ILWS-2011 Workshop "Towards the Next Solar Maximum"
30 August 2011
Beijing, China
Arcade Flare Irradiances
Correlations of rise time in SXR with
(1) flare duration,
(2) delay in EUV peak irradiances,
and (3) GOES magnitude
ILWS-2011 Workshop "Towards the Next Solar Maximum"
30 August 2011
Beijing, China
Irradiance Flare Peak Width
ILWS-2011 Workshop "Towards the Next Solar Maximum"
30 August 2011
Beijing, China
Impulsive Phase
Measured by He II 30.4 nm
C1.0+
ILWS-2011 Workshop "Towards the Next Solar Maximum"
C4.0+
30 August 2011
Beijing, China