# Presentation: 816234

##   Super-rotation of Supergranulation:             The Sun does “The Wave”

- Supergranulation
- Pattern of horizontal outflows, outlined by network of magnetic features
- Distinct scale of 30 Mm; lifetime:  1 day
- Dynamics poorly understood, but believed to correspond to a preferred ‘cellular’ scale of thermal convection
***Puzzle for over 20 years: Why does supergranulation appear to rotate faster around the Sun than the magnetic features and the plasma?**** *
- Analysis of MDI observations shows that** *****supergranulation undergoes oscillations and supports waves*** with periods of 6-9 days
***Waves are predominantly prograde***, which explains the super-rotation of the pattern        (cf. “The Wave” in a soccer stadium)
- Gizon et al., 2003, Nature 421, p.43

- SOHO/MDI movie of solar supergranulation
- (10 day sequence at 15 min image cadence)** **** **

##   Subsurface Structure of Sunspots

- How can sunspots last for several weeks without flying apart?
- Models: inflows
- Observations at surface: outflows!
- Applying the new technique of acoustic tomography to high quality MDI data provided first images of the thermal structure and flows around sunspots *below* the surface.
- Strong inward flows right underneath the surface
- Sunspots surprisingly shallow: become warmer than surroundings already some 4000 km below surface

**Zhao et al.: 2001, ApJ 557, 384**

##   SOHO Multi-Instrument Observations   of X1-flare of 21 April 2002

- Long-duration X1 proton flare on 21 April 2002, 01:51 UT, from Active Region NOAA 9906
- Associated with a very fast coronal mass ejection (CME) and moderate proton storm
- SOHO was running a multi-instrument flare campaign on this target region, coordinated with TRACE, RHESSI and several ground-based observatories

**  ****The flare as seen by TRACE – ****the “13****th**** instrument on SOHO”**

##         SOHO/TRACE/RHESSI Multi-Instrument        	Observations of X1-flare of 21 April 2002

##   SOHO Multi-Instrument Observations   of X1-flare of 21 April 2002

- Spectroscopic observations of the CME by UVCS
- Time-series images in four UV emission lines, showing threads of ejected material at very different temperatures
- Spectroscopic observations of the flare by SUMER
- Animation showing the location of the SUMER slit above the limb and the time evolution of the hot Fe XXI line.
- Stills show time evolution maps (intensity and velocity). Velocities reaching 300 km/s were observed
- Note the pronounced Doppler oscillations at flare onset

##   Twanging the Sun’s Guitar:                          Hot Loop Oscillations

- SUMER discovery: strong Doppler oscillations (±300 km/s) in hot loops above active regions
- Typical periods: 10-20 min, with comparable decay time scales
- Only seen in hot flare lines (> 6 MK, e.g. Fe XVII, Fe XIX, Fe XXI)
- Nature of oscillation modes still unclear
- Prospect of probing coronal structure by *“coronal seismology”*

**Fe XIX**

**EIT:       Fe XII    195 ****Å**
**SUMER: Fe XIX 1118 Å**

##       UV/EUV Spectral Atlas 670 – 1609Å

- Best ever analysis of the ultraviolet spectrum of the Sun from 670 to 1609 Å
- 1100 emission lines identified
- 150 of these had not been recorded or identified before
- Particular improvement for Å
- Atlas contains spectra of the quiet Sun, a coronal hole, and a sunspot.
- Rich source of new diagnostic tools to study physical parameters in the solar atmosphere.
- Important product both for solar and stellar communities.

**Curdt et al.: 2001, A&A 375, 591**

##                    Water Production of 			Comet C/1999 S4 (LINEAR)

**SWAN observed hydrogen coma of comet C/1999 S4 from end of May through mid August 2000**
**Obtained systematic set of water production rates for this well documented event of complete fragmentation of a cometary nucleus.**
**Total amount of water released: 3.3x10****9**** kg**
**Combining the SWAN measurements  with Hubble observations of the last fragements yields estimate for size of comet: r = 375 m **
**and thus estimate of density:             ******** 15 kg/m****3**

**SWAN observations of Comet LINEAR a month before it disintegrated.**

**Fragments of Comet Linear seen as mini-comets by HST on         5 August 2000.**

**M****äkinen et al.: 2001, Science 292, 1326**

## Inflows in the Corona

- LASCO discovery: inflows at distances of  2 - 4 R
- Speeds: 20 km/s to over 100 km/s
- Mostly decelerated or nearly uniform inward motion
- Inflow rate correlated with the occurrence of non-polar coronal holes and other indicators of nonaxisymmetric open flux.
- Origin?
- Gradual closing-down of magnetic flux dragged outward by CME? Collapsing field lines?
- Key role for balance of Sun’s open magnetic flux

**Sheeley & Wang: 2001, ApJ 562, L107**

##       CMEs: Current Sheets & Flux Ropes

- UVCS, EIT, and LASCO observed a CME on 23 March 1998 that exhibited narrow, extremely hot ***(> 6x10******6******K)*** plasma emitting in Fe XVIII.
- This emission occurred a the expected location of a ***current sheet*** predicted by the model of Forbes & Lin (2000).
- Fe XVIII emission occurs between the post-CME arches on the limb and the CME itself.
- The current sheet predicted by Forbes & Lin has a lifetime and spatial scale that is consistent with the spectroscopic constraints.

## Synoptic Imaging of the                                  Far Side of the Sun

**Synoptic maps combining observed magnetic flux from the near-side of the Sun with proxy flux from the far-side inferred from sound travel time analysis**
**Data: medium-l MDI data**
**Technique: two-skip helioseismic holography (Lindsey & Braun, Science 2000)**
**Updated daily on Internet**

##   The Event of 24 September 20014th Largest Proton Storm of the Current Solar Cycle