# Presentation: 874245

## Evidence for Wave Mode Conversion in the Solar Chromosphere?

- B. Fleck1, J. Armstrong2, A. Cacciani3, B. De Pontieu4, W. Finsterle5, S.M. Jefferies2, S.W. McIntosh6, T.D. Tarbell4
*1**ESA Research and Scientific Support Department*
*2**Maui Scientific Research Center / Univ. of New Mexico*
*3**Universita degli Studi di Roma “La Sapienza”*
*4**Lockheed Martin Solar and Astrophysics Lab*
*5**PMOD/WRC Davos*
*6**SwRI Boulder*

## Travel Time and Phase Analysis of Waves in the Lower Solar Chromosphere

- B. Fleck1, J. Armstrong2, A. Cacciani3, B. De Pontieu4, W. Finsterle5, S.M. Jefferies2, S.W. McIntosh6, T.D. Tarbell4
*1**ESA Research and Scientific Support Department*
*2**Maui Scientific Research Center / Univ. of New Mexico*
*3**Universita degli Studi di Roma “La Sapienza”*
*4**Lockheed Martin Solar and Astrophysics Lab*
*5**PMOD/WRC Davos*
*6**SwRI Boulder*

## Data

| Observatory | VTT Sac Peak | MOTH | SVST |
| --- | --- | --- | --- |
| Date of Observations | 1989/08/31 | 2003/01/20 | 1992/06/30 |
| Lines | Na D1, Fe I 5930 | Na D2, K I | Na D1, Fe I 5576, Hα |
| Duration  | 3 hours | 4 h 45 min | 1 h 15 min |
| Cadence | 10 s | 10 s | 46 s |
| Spatial Resolution | 0.611”/pixel | 5.5”/pixel | 0.137”/pixel |

## Integrated V-V Phase, Coherence & Power Spectra

-             Sac Peak                                  MOTH                                       SVST

## Integrated Na V-I Phase, Coherence & Power Spectra

-             Sac Peak                                  MOTH                                       SVST

## Integrated Fe V-I Phase, Coherence & Power Spectra

-             Sac Peak                                  MOTH                                       SVST

## k- V-V Phase Diagram

-  Negative phase below 2 mHz not restricted to certain k range
-  Surprise that ridge/inter ridge regimes have different signs! Model?

## Field of View / TopologySVST Data

## Travel Time Maps Na V – Fe V (SVST Data)

## Coherence Maps Na V - Fe VSVST Data

## Power Maps Na VelocitySVST Data

## Power Maps Fe VelocitySVST Data

## Field of View / TopologyMOTH Data

## Travel Time Maps Na V - K VMOTH Data

## Coherence Maps Na V - K VMOTH Data

## Power Maps Na VelocityMOTH Data

## Power Maps K VelocityMOTH Data

## Results 1

- Integrated V-V spectra
- Show expected behaviour in 2-10 mHz range (evanescent  running acoustic waves)
- f < 2 mHz:
- Sac Peak: signature of gravity waves
- MOTH: different sign; cause?
- SVST data: time resolution and duration marginal
- MOTH spectra validate quality of MOTH velocity measurements
- Integrated V-I spectra
- Striking difference between Sac Peak, MOTH, and SVST data   “contamination” of intensity signal in filtergraph series?
- Conspicious phase jump and drop in coherence at 2 mHz, in particular in MOTH data; origin?

## Results 2

- Travel-Time Maps
- Wave propagation behaviour significantly changed in and near magnetic field regions
- 3-5 mHz band (“evanescent regime”):
- Upward propagation with significant time lag in strong field regions, while evanescent waves (high phase speed, small travel times) in quiet sun
- f > 5 mHz (i.e. > fcut-off)
- small time lag (and in some cases even downward propagation) in magnetic field regions, while quiet sun showing expected behaviour of upward propagating sound waves
*Mode conversion and/or wave reflection at ****=1 surface?*
- Power Maps
- Significantly reduced power in magnetic field regions, with enhanced power “halos” at f > 6 mHz
- Next steps: **modelling** (cf. Carlsson et al.)