investigating euv dimming/cme/icme events - source properties … · 2019. 1. 11. · fall 2018 agu...

Investigating EUV Dimming/CME/ICME

Events - Source Properties and IP Effects

D. Webb1, A. Reinard2, J. Mason3, L. Krista4, B. Thompson3

(1) Boston College/ ISR, Chestnut Hill, MA, USA

(2) NOAA/ SWPC, Boulder, CO, USA

(3) NASA/ Goddard Space Flight Center, Greenbelt, MD USA

(4) University of Colorado/ CIRES, Boulder, CO, USA

Fall 2018 AGU Meeting

Washington, DC

14 December 2018

14 Dec 2018 DFW FaAGU Wash. DC 2

• Program: Better understand initiation, development, and evolution of transient

coronal dimming regions and their relationship to CMEs and ICMEs.

• Goal: Establish/ confirm relationship(s) between the dimming parameters and CMEs,

then extend to their ICME parameters and geostorm occurrence and level.

• What is New? Assemble dimmings assoc. with CMEs that can be tracked from the

Sun to L1/Earth.

• Data selection:

- Flare/dimmings assoc. with Earthward CMEs during SDO period 2010 - 2014;

covers period when EVE MEGS-A was operational for full Fe spectra.

- Good IP tracking of CMEs from Sun to L1.

a) Period of 2010 ~ 2012 when STEREOs at quadrature allowing good tracking with HIs

(STEREOs bet. 60 and 120 from Sun-Earth line from Nov. 2009 to Sept. 2012).

b) Based on studies by Wood+ (JGR 2016; ApJSS 2017) and Moestl+ (ApJ 2014)

- Compare parameters of dimmings and their CMEs with assoc. ICMEs:

a) ICME identifications from online Richardson & Cane list:

http://www.srl.caltech.edu/ACE/ASC/DATA/level3/icmetable2.htm

b) Composition and charge state data from ACE/SWICS:

http://www.srl.caltech.edu/ACE/ASC/level2/lvl2DATA_SWICS-SWIMS.html

• We have identified and are studying 18 dimming-CME-ICME events.

- Today we show statistical comparisons among these 3 groups.

- Work in progress!

Outline

What are Coronal

Dimmings?

12 May 1997 SOHO/EIT 195Å

04:34 UT 05:24 UT

- Localized decreases in emission,

typically in EUV.

- Usually assoc. with a flare & CME

& often a coronal wave.

- Have variety of shapes & extents

with timescales/ lifetimes of

minutes to hours.

- Two categories of dimmings:

Core: Assoc. with mass loss of

eruption from core loops; near

flare/CME location.

Secondary: Reduced, more global

emission due to expansion of CME

& assoc. fields.

- Dimmings usually recover to

original emission level Lifetimes

vary from minutes to 2 days with a

mean of ~8 hrs (EIT - Reinard &

Biesecker, ApJ 2008) or ~20 hrs

(SXT – Kahler & Hudson 2001).

23 April 1998

- When present, dimmings appear to be best

indicator of location and extent of the WL CME.

- May trace field lines opened during a CME and

the mass and magnetic flux transported outward.

Help improve our physical understanding of CMEs

and associated phenomena.

x

Why Study Dimmings?

- Some dimming studies: Thompson+, 2002; Bewsher+, 2008; Reinard & Biesecker,

2008; 2009; Aschwanden 2016; Mason+, 2016; Krista & Reinard, 2017; Graz group –

Dissauer+, 2018a,b,c.

Recent Coronal Dimming Catalogs • Based on automatic or semi-automatic identifications

• Use Solar Dynamics Observatory (SDO) observations beginning in April 2010

• We use results from all of these in our study.

- Coronal Dimming Tracker (CoDiT) – Krista & Reinard (ApJ 2017)

Uses SDO/Atmospheric Imaging Assembly (AIA) 193Å and Helioseismic &

magnetic Imager (HMI) observations to semi-automatically measure dimmings and

their magnetic fields.

- Solar Demon – Kraaikamp & Verbeeck (JSWSC 2015)

Uses AIA 211Å images to automatically measure dimmings (and waves).

- James’s-EVE-Dimming-Index (JEDI) – Mason+ (ApJ 2014; ApJ 2016)

Uses SDO/ EUV Variability Experiment (EVE) irradiance data to spectrally detect

dimmings.

- Graz group catalog – Dissauer+ (ApJ 2018 a, b, c)

~60 dimmings using AIA, HMI and STEREO/SECCHI observations semi-

automatic measurements of them, their magnetic fields and assoc. CMEs.


2011 February 15 Event Illustrates Our Method X2 flare + dimming in AIA 193Å | CoDiT area vs time

AIA 193Å flare + dim.; LASCO C2 halo CME

STEREO/SECCHI images with 3D reconstructions

showing tracking SunEarth; Wood+ 2017

3D fit at L1 | Wind n, V, B at L1. Red=pred. Green=actual FR


Solar Disk Locations of the Dimmings

Centroid locations of

the 18 (core)

dimmings of our

study. Red circles

single dimming

events; blue circles

two dimming areas

assoc. with a

CME/ICME.


Comparisons of Dimming Areas

DEMON

(this study)

Reinard & Biesecker (2008)

Dissauer+ (2018c)

Red = “weak” CMEs

CoDiT

(this study)

Comparisons of Dimming Lifetimes (top) &

Dimming Areas vs Lifetimes (bottom)

R&B (2008)

Krista & Reinard (2017)

• Top plots our dimming lifetimes are a few to tens of hours, similar to previous results.

• Bottom plots show CoDiT results: (Left) Study of 154 AIA-193Å dimmings in 2013 dimming lifetimes and

areas are highly correlated. (Right) Our result is similar.

CoDiT

(this study)

CoDiT

(this study)

Dimming events more likely to be

associated with large flares. All CMEs

with speeds > 800 km/s have dimmings.

CME speed vs. flare energy

dimming and non-dimming events

Dimming (SOHO/EIT) vs CME (LASCO) Results;

Reinard & Biesecker (ApJ, 2009)

CME speed vs. max. dimming area

Weak correlation tendency for

larger dimmings to be assoc. with

faster CMEs (cc = 0.46).


Dimming (SDO/EVE) vs CME (LASCO-SECCHI

3D) Parameters; Mason+ (ApJ, 2016)

• Example of fitting of EVE irradiance dimming

parameters: slope, depth, duration

• Comparison with expected CME parameters:

speed vs slope; mass vs depth

Dimming (SDO/AIA/HMI) vs CME (STEREO/SECCHI)

Parameters; Dissauer+ (ApJ, 2018c)

• Good corr. bet. dimming intensity (area

+ depth) and CME speed; agrees with

Mason+ result and R&B tendency.

• Since intensity column density

faster CMEs originate lower in corona.

• Good corr. bet. dimming area and CME

mass; agrees with Mason+ tendency.

• Dissauer+ (2018b) also find that both

dimming intensity and area are strongly

corr. with total magnetic flux.


Comparisons with CME Speeds & Masses (this study)

• CME speed compared with DEMON depth (left), area (middle) and CoDiT area (right).

• All show good correlations confirming the prior statistical results. Note the high speed outlier (7 March 2012).

• CME mass compared with DEMON depth (left), area (middle) and CoDiT area (right).

• Tendency for dimming depth/area to be assoc. with CME mass but correlations not strong. Perhaps not surprising

because many of our CMEs are halos masses have large uncertainties & not corrected for projection effects.

14 Dec 2018 DFW FaAGU Wash. DC

• ICME magnetic field compared with DEMON dimming duration (left) and depth (middle). Right:

ICME speed vs dimming duration.

• These show weak correlations. ICME proton densities vs dimming parameters exhibit only poor

correlations.

Comparisons with In-situ ICME Parameters (this study)

… and with Geostorms (Dst)

• So far we have found only poor correlations between any dimming, CME or ICME parameter and

the Dst index.

• Future work: Examine the events on a case by case basis to better understand this null result.


• The dimming-Fe/O comparison also is

of interest. A good correlation

suggests dimmings represent plasma

pulled from lower in the solar

atmosphere, where heavier elements

more prevalent.

• Left are Fe/O vs dimming area plots

for our DEMON and CoDiT data.

• Tendency for dimming areas to be

assoc. with increased Fe/O, but lots

of scatter.

• Enhanced helium abundance has been found in ICME material.

• Our dimming lifetimes vs alpha/proton plots for the DEMON (left) and CoDiT (middle) data. Compared with prior

unpublished sample from R&B (2009) study (right), our area, intensity & depth plots show less scatter.

• Tendency for dimming lifetimes to be assoc. with increased helium abundance.

Comparisons with in-situ ICME composition (this study)

Conclusions • Coronal dimmings trace field lines opened during a CME and the mass and magnetic flux

transported outward.

- Goal understand development of coronal dimming regions and their relationship to

CMEs, ICMEs and geostorms.

• The distributions of our dimming parameters, such as maximum area and lifetimes, similar to

previous statistical studies.

• Comparisons of our dimming depth & area with CME speed & mass show good to moderate

correlations, confirming prior statistical results. Future work correct the CME speeds &

masses for projection effects, esp. halos, producing 3D parameters.

• Comparisons of our dimming parameters to ICME magnetic fields and speeds show weak

correlations. The correlations with ICME proton density are poor.

• Comparisons of dimmings with composition parameters, /p and Fe/O:

- Tendency for dimming lifetimes to be assoc. with increased helium abundance, as

expected for ICME material.

- Tendency for dimming areas to be assoc. with increased Fe/O, but lots of scatter.

• Only poor correlations between any dimming, CME or ICME parameter and the Dst index.

- Future work

• Although we were careful to include only significant dimmings assoc. with CMEs well tracked

from Sun to 1 AU, the total number ~20 small for statistical work. Add more events: Future work

14 Dec 2018 DFW FaAGU Wash. DC

Thanks for Listening!

Kudos to Thomas Kuchar for help with data analysis.

This work is supported by NASA grant NNX15AR06G through GSFC.

[email protected]

17 DFW FaAGU Wash. DC 14 Dec 2018

investigating euv dimming/cme/icme events - source properties … · 2019. 1. 11. · fall 2018 agu...

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