Solar Cycle 24 Group G

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(New page: == Introduction == Calculation show that Hinode/XRT lower limit on energy (with temperature discimination) ~7x10^23 erg (T=2 MK). Microflares so what * small events are numerous, can be ...)
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Hinode allocations, SOT (70%), EIS (15%), XRT (15%).  Averaging multiple frames (hours worth) yields much higher signal to noise.  Gradient of that image shows many interesting structures.  Geyser are defined as jets that go off multiple times.  XRT observes small scale brightenings which are being called nanoflares for now.  A peak finding algorithm can find active pixels.  Bright points are found to be more active than dimmer regions.  Occur more in network boundaries.  Using a filter ratio method than one particular event gives an temperature of 1.5 MK.  Luminosity distribution shows a power law with an index of -2.24 but multipixel events are counted multiple times which would make it too steep.
Hinode allocations, SOT (70%), EIS (15%), XRT (15%).  Averaging multiple frames (hours worth) yields much higher signal to noise.  Gradient of that image shows many interesting structures.  Geyser are defined as jets that go off multiple times.  XRT observes small scale brightenings which are being called nanoflares for now.  A peak finding algorithm can find active pixels.  Bright points are found to be more active than dimmer regions.  Occur more in network boundaries.  Using a filter ratio method than one particular event gives an temperature of 1.5 MK.  Luminosity distribution shows a power law with an index of -2.24 but multipixel events are counted multiple times which would make it too steep.
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== Observations of the Thermal and Dynamic Evolution of a solar microflare by J. Brosius ==
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New CDS staring mode with rapid cadence applied to compact GOES B2 flare also observed by EIT MDI, TRACE (1600 angstrom), RHESSI.  Sources from EIT and RHESSI are offset by 7 arcseconds both near a small emerging magnetic island.  TRACE image show complex structure...loops?  ribbons?  Relative doppler velocities observed at -15 to -20 km/s.  Peaks in Fe XIX, Si XII, O V lines coicident in time with flare.  Upflows are consistent with chromospheric evaporation (gentle evaporation not explosive).  RHESSI observations show little or no nonthermal spectrum but with temperature of approx. 11 MK (pretty usual for a microflare).  Analysis on another event is ongoing.  For an M class flare, doppler velocities are -100 km/s but now explosive evaporation along with a gentle evaporation later on in the flare. 
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== Hot Plasma in non-flaring active regions by Paola Testa ==
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Testing nanoflare heating models (Real et al. 2008).  Hot plasma in nonflaring ARs is thought to be heated by nanoflares.  Predictions suggest hot plasma should exist (Klimchuk 2008).  Using Hinode/EIS it is possible to check this.  Unfortunately, temperature diagnostics with filters can be difficult and calibration is ongoing (for Be_med and Al_med).  Filter rations give very hot temperatures 10^(7.5) K.  Blending of lines is also an issue.  Deblending of lines is necessary.  A procedure is described by Young et al. 2006.  These methods are being tested.  If the temperatures are really that high then RHESSI should be able to see it so can use RHESSI to set a maximum temperature possible.

Revision as of 02:26, 10 December 2008

Contents

Introduction

Calculation show that Hinode/XRT lower limit on energy (with temperature discimination) ~7x10^23 erg (T=2 MK).

Microflares so what

why now?

who cares?

Polar X-ray Jets

Does not matter where in coronal hole you are for where the jets occur (no latitude dependence). Associated with increases in soft x-rays (maybe also observed with RHESSI?). Energy is 1027 erg for these SXR events. Larger polar jet also observed on the coronagraph. Transverse motion from direction of jet is usual. Statistics of jets (about 100 jets)...average duration approx. 800 sec. (as defined by the SXR source), average size 0.8 Mm (Savcheva 2007). Histogram of velocity distribution has peak at approx. 140 km/s. Cirtain et al (2007) show outflows of 800 km/s. Jets formed on the south pole 60% likely to more eastward. SXR sources can shoot out multiple jets or just one before fading. These events seem similar to jets seen in active regions where the SXR source can be associated with a flare...maybe? Great multifilter observation of jet suggests cooling time is blackbody. Outflow component is millions of kelvin.

frequency of jet formation 7 per hour per coronal hole derived from 1418 and 120 hours of observation.

Jets in ARs and quiet Sun may be different since quiet sun jets do not have to contend with closed magnetic fields.

The Quiet Sun that wasn't by P. Grigis

Hinode allocations, SOT (70%), EIS (15%), XRT (15%). Averaging multiple frames (hours worth) yields much higher signal to noise. Gradient of that image shows many interesting structures. Geyser are defined as jets that go off multiple times. XRT observes small scale brightenings which are being called nanoflares for now. A peak finding algorithm can find active pixels. Bright points are found to be more active than dimmer regions. Occur more in network boundaries. Using a filter ratio method than one particular event gives an temperature of 1.5 MK. Luminosity distribution shows a power law with an index of -2.24 but multipixel events are counted multiple times which would make it too steep.

Observations of the Thermal and Dynamic Evolution of a solar microflare by J. Brosius

New CDS staring mode with rapid cadence applied to compact GOES B2 flare also observed by EIT MDI, TRACE (1600 angstrom), RHESSI. Sources from EIT and RHESSI are offset by 7 arcseconds both near a small emerging magnetic island. TRACE image show complex structure...loops? ribbons? Relative doppler velocities observed at -15 to -20 km/s. Peaks in Fe XIX, Si XII, O V lines coicident in time with flare. Upflows are consistent with chromospheric evaporation (gentle evaporation not explosive). RHESSI observations show little or no nonthermal spectrum but with temperature of approx. 11 MK (pretty usual for a microflare). Analysis on another event is ongoing. For an M class flare, doppler velocities are -100 km/s but now explosive evaporation along with a gentle evaporation later on in the flare.

Hot Plasma in non-flaring active regions by Paola Testa

Testing nanoflare heating models (Real et al. 2008). Hot plasma in nonflaring ARs is thought to be heated by nanoflares. Predictions suggest hot plasma should exist (Klimchuk 2008). Using Hinode/EIS it is possible to check this. Unfortunately, temperature diagnostics with filters can be difficult and calibration is ongoing (for Be_med and Al_med). Filter rations give very hot temperatures 10^(7.5) K. Blending of lines is also an issue. Deblending of lines is necessary. A procedure is described by Young et al. 2006. These methods are being tested. If the temperatures are really that high then RHESSI should be able to see it so can use RHESSI to set a maximum temperature possible.

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