# Presentation: 807669

## Comparison of Blinkers and Explosive Events

**Danielle Bewsher **
**(dbewsher@esa.nascom.nasa.gov)**
**ESA Space Science Dept, NASA/GSFC, USA**
**Davina Innes**
**Max-Planck-Institute fur Aeronomie, Lindau, Germany**
**Clare Parnell**
**University of St Andrews, St Andrews, Scotland**

## Introduction - Blinkers

**Small bright intensity enhancements **
**Seen in EUV lines, e.g. O V, O IV (SOHO/CDS), He II (SOHO/EIT) **
**Discovered by eye using SOHO/CDS (Harrison, 1997; Harrison et al., 1999)**
**More recently automated identification methods developed (Brkovi****ć, Solanki and Rüedi, 2001; Bewsher, Parnell and Harrison, 2002)**
**Events found throughout**
- Quiet Sun (Bewsher, Parnell and Harrison, 2002)
- Active Region (Parnell, Bewsher and Harrison, 2002)
**Believed to be enhancements in density or filling factor, not temperature**
**Preferentially occur above large or strong magnetic fragments**
**Doppler and non-thermal velocities are preferentially more red-shifted and greater than normal transition region plasma **

## Introduction – Explosive Events

**Broadened and/or shifted line profiles**
**Observed in EUV lines**
**Discovered with HRTS (Brueckner and Bartoe, 1983), more recently observed with SOHO/SUMER**
**Found in Quiet Sun, Active Regions and Coronal Holes**
**Believed to be caused by magnetic reconnection  (Innes et al., 1997) during cancellation of photospheric field with emerging flux (Dere et al., 1991) or dissipating AR flux (Porter & Dere, 1991) **
**Occur above regions of mixed polarity field near magnetic neutral lines (Chae, Yun & Poland, 1998)**

## Blinker & Explosive Event I –SUMER & CDS images

**Explosive Event (S1) at top of SUMER single slit image**
**3 Blinkers (C1, C2, C3) observed at top of CDS raster along SUMER slit**
**◊ ****- midpoint of blinkers**
**Dashed line – position of SUMER slit**
**Only example of co-spatial and co-temporal blinker and explosive event**

## Blinker & Explosive Event II -SUMER & CDS lightcurves

**Solid lines show lightcurve of SUMER region S1 and blinker C2**** **
**Dashed line shows the lightcurve of the CDS region that refers directly to the SUMER region S1**
**Times ****t1****, ****t2**** and ****t3**** refer to the time before, the time of and the time after the CDS raster shown on the previous slide**
**• ****- mark start and end of blinker**
**Evidence of blinker seen in SUMER lightcurve?**

## Blinker & Explosive Event III – SUMER & CDS line profiles

**Times ****t1****, ****t2**** and ****t3**** refer to the time before, the time of and the time after the CDS raster shown previously**
**Explosive Event can be seen clearly in the SUMER line profile as line shift and enhanced wings**
**Blinker can be seen in CDS line profile as increase in line amplitude**
**No evidence of explosive event in CDS line profile**

## Blinker & Explosive Event IV –More CDS lightcurves & line profiles

## Blinker & no Explosive Event I –SUMER & CDS images

**2 brightenings (S2, S3) seen in SUMER single slit image, but no explosive events**
**2 blinkers (C4, C5) lie along SUMER slit in CDS raster**
**◊**** ****- midpoint of blinkers**
**Dashed line – position of SUMER slit**
**2 examples out of ten where blinkers are present and explosive events are not**

## Blinker & no Explosive Event II –SUMER & CDS lightcurves

**Solid lines show SUMER region S2 and lightcurve of blinker C4**
**Dashed line shows lightcurve of CDS pixels that directly refer to the SUMER region S2 **
**• ****- mark start and end of blinker**
**Times ****t1****, ****t2**** and ****t3**** refer to the time before, time of, and the time after the CDS raster shown on the previous slide  **
**Evidence of blinker in SUMER lightcurve?**

## Blinker & no Explosive Event III –SUMER & CDS line profiles

**Times**** t1****, ****t2**** and ****t3****, refer to the time before, the time of and the time after the CDS raster shown previously**
**Intensity enhancements seen in both SUMER and CDS line profiles at different times**
**No evidence of significant line shift or broadening in either SUMER or CDS line profiles**

## Blinker & no Explosive Event IV – SUMER & CDS lightcurves

**Solid lines show SUMER region S3 and lightcurve of blinker C5**
**Dashed line shows lightcurve of CDS pixels that directly refer to the SUMER region S3 **
**• ****- mark start and end of blinker**
**Times ****t1****, ****t2**** and ****t3**** refer to the time before, time of, and the time after the CDS raster shown on the previous slide**
**Evidence of blinker in SUMER lightcurve?**

## Blinker & no Explosive Event V –SUMER & CDS line profiles

**Times**** t1****, ****t2**** and ****t3****, refer to the time before, the time of and the time after the CDS raster shown previously**
**Small changes in intesity as blinker reaches the end of its lifetime**
**SUMER lightcurve and line profile shows an increase in intensity at time ****t2****, which is not visible in CDS**
**No evidence of significant line shift or broadening seen in the SUMER or CDS line profiles**

## Explosive Event & no Blinker I –SUMER & CDS images

**Explosive event, S4, seen at top of SUMER single slit image**
**No blinker seen at corresponding position, C6, in CDS raster**
**◊**** ****- midpoint of blinkers**
**Dashed line – position of SUMER slit**
**One of seven examples where an explosive event is observed but no associated blinkers are seen **

## Explosive Event & no Blinker II –SUMER & CDS lightcurves

**Solid lines show SUMER region S3 and lightcurve of blinker C5**
**Dashed line shows lightcurve of CDS pixels that directly refer to the SUMER region S3 **
**Times ****t1****, ****t2**** and ****t3**** refer to the time before, time of, and the time after the CDS raster shown on the previous slide**
**Intensity enhancement seen in SUMER – but the CDS lightcurve does not meet the criteria for a blinker**

## Explosive Event & no Blinker III –SUMER & CDS line profiles

**Times**** t1****, ****t2**** and ****t3****, refer to the time before, the time of and the time after the CDS raster shown previously**
**Explosive event can be seen as enhancement in both red and blue wings of SUMER profiles **
**No evidence of explosive event in CDS line profiles**

## Discussion

**Only one co-incident and co-spatial blinker and explosive event**
- What are the chances that a blinker and an explosive event could randomly occur together?
**Evidence of blinkers seen in SUMER lightcurves**
- Would they meet the same criteria for identifying blinkers?
- Would one event or many smaller/shorter lived events be found?
**No evidence of explosive events (significant line shifts or broadenings) in CDS blinker line profiles**
- Would we expect to see them given the resolution of CDS?
- Would we see significant shifts/broadenings in the individual pixels that make up the blinker?
**Is the same mechanism responsible for both blinkers and explosive event?**
**What is causing the 3 different scenarios (blinker only, explosive event only, and both blinker and explosive event) to occur?**

## References

**Bewsher, D., Parnell, C.E., Harrison, R.A. : 2002, Solar Phys., 206, 21.**
**Brkovi****ć****, A., Solanki, S., R****ü****edi, I. : 2001, A&A, 373, 1056.**
**Brueckner, G., Bartoe, J.-D. : 1983, ApJ, 272, 329.**
**Chae, J., Yun, H., Poland, A. : 1998, ApJ Sup, 114, 151. **
**Dere, K., Bartoe, J.-D., Brueckner, G., Ewing, J., Lund, P. : 1991, JGR, 96, 9399.**
**Harrison, R.A. : 1997, Solar Phys., 175, 467.**
**Harrison R.A., Lang, J., Brooks, D., Innes, D. : 1999, A&A, 351, 1115.**
**Innes, D., Inhester, B., Axford, W., Wilhelm, K. : 1997, Science, 386, 811.**
**Innes, D. : 2002, A&A, 378, 1067.**
**Parnell, C.E., Bewsher, D., Harrison, R.A. : 2002, Solar Phys., 206, 249.**
**Porter, J., Dere, K. : 1991, ApJ, 370, 775.**

**Data used is courtesy of SOHO/CDS and SOHO/SUMER consortiums. SOHO is a project of international cooperation between ESA and NASA**

## Properties of Blinkers & Explosive Events

| Property | QS Blinkers | AR Blinkers | Explosive Events |
| --- | --- | --- | --- |
| Global Frequency (s-1) | 10.8 | 13.7 | Approx 600 |
| Mean Intensity Enhancement Factor | 1.9 | 2.4 | 2.0 – 5.0 |
| Mean Area (x 10 km2) | 2.7 | 3.9 | Approx 0.1 |
| Mean Lifetime (minutes) | 19.2 | 17.5 | 1.0 – 6.0 |
| Maximum Doppler Velocity (km s-1) | 30.0 | 40.0 |  |
| Maximum Non-Thermal Velocity (km s-1) | 45.0 | 45.0 |  |