HOP 0241

abstract of observational proposal

INTRODUCTION: Flare observations at 10 s cadence with CDS stare studies PBEAM and FLAREDOP have provided valuable insight into the physics of flares and microflares. This prompted the development of the EIS rapid cadence (11.2 s) flare stare study FLAREDOP_EIS (ID# 472), which has successfully observed several microflares (GOES levelC1 or weaker) as of this writing (Brosius 2013, ApJ 762, 133; Brosius 2013, ApJ 777, 135; see also EIS Nuggets from November 2012 and November 2013). Here we propose to obtain rapid cadence EIS stare spectra (FLAREDOP_EIS) coordinated with rapid cadence IRIS stare spectra, along with filter images from XRT and longitudinal magnetograms from SOT. Coordinated observations with CDS will be
sought as long as CDS continues to operate.

SCIENCE OBJECTIVES: Flare emission originates in plasma over a wide range of temperatures, from those characteristic of the chromosphere (~0.01 MK) to those uniquely associated with flares (~10 MK), and canevolve on timescales of seconds. We propose to observe flares with EIS using the rapid cadence (11.2 s) flare stare study that we developed (FLAREDOP_EIS, ID# 472). This study is designed to measure(1) time differences in the brightenings of lines formed at differenttemperatures (which indicates whether flare energy transport is dominated by nonthermal particle beams or by thermal conduction); (2) the evolution of flare physical properties like electron density (based on density-sensitive line intensity ratios), bulk flows (based on Doppler shifts of whole line profiles and/or the emergence of secondary, highly shifted components), and unresolved turbulent motions (based on nonthermal line widths). The EIS spectra will be combined with slit-jaw images and FUV spectra from NASA's IRIS satellite in order to expand the spatial and temperature coverage of EIS alone. These coordinated observations are unique in that they provide simultaneous, rapid cadence spectra covering a wide temperature range at 2 different locations within a flaring source. If CDS is able to participate, we will potentially observe solar flares simultaneously with three different spectrometers pointed at three different locations within the source region. We hope to observe event(s) sufficiently energetic (greater than GOES level C1) that RHESSI will provide not only evidence for nonthermal electrons, but also measurements of their properties.

request to EIS

OBSERVATIONS: Please run FLAREDOP_EIS (ID# 472) four times in succession (3 h, 44 m), with tracking, on a suitable active region (one with a reasonable probability of flaring) daily for one week. The data volume of FLAREDOP_EIS is 168.5 Mbits. The EIS CO should select the target active region, and broadcast the selection to the XRT, SOT, IRIS, and CDS planners so they can make appropriate plans for coordinated observations as early as possible. For context please also run the EIS slot study 353 (PRY_slot_context_v3, data volume of 4.9 Mbits) before the start of the first run of FLAREDOP_EIS, and again after the end of its last run during a given series of runs. We request XRT and SOT observations of the same active region observed by EIS, IRIS, and CDS, with fields of view that cover nearly the entire active region. The EIS (184 arcsec) and IRIS (175 arcsec) slit segments proposed for this investigation are similar, so we request fields of view about 3 arcmin by 3 arcmin for both SOT and XRT. From SOT we request longitudinal magnetograms and Ca II images at 1 minute cadence. From XRT we request 20 s cadence in each of 3 filters that provide the broadest possible temperature coverage, including flare temperatures around 10 MK.

Please run FLAREDOP_EIS (ID# 472) four times in succession (3 h, 44 m), with tracking, on a suitable active region (one with a reasonableprobability of flaring) daily for one week. For context please also run the EIS slot study 353 (PRY_slot_context_v3, data volume of 4.9 Mbits) before the start of the first run of FLAREDOP_EIS, and again after the end of its last run during a given series of runs. A different region can be selected each day.

other participating instruments

IRIS

Run a very large sit-and-stare (OBS-ID 4), with the IRIS slit offset about 30 arcsec from that of EIS. Please try to achieve 10 s cadencein an AR observation that includes Fe XXI, Fe XII, O IV (both 1399 and 1401 for density diagnostics), Si IV, and C II; 30 s cadence would be acceptable if necessary to achieve reasonable count rates for coronal lines. Perform with solar rotation tracking to maintain constant separation from the EIS slit. Please observe the target region for 4 hours while EIS observes the same.

We will include RHESSI observations in our analysis when those observations are available. Because SDO observes the Sun nearly continuously from its inclined geosynchronous orbit, coordinated observations with AIA are expected for most events. We request a pointing offset between CDS (FLAREDOP/167/v3), EIS, and IRIS so that spectral line observations will be acquired at three different locations within the target region.

remarks

Since SOHO/CDS is at present bein run with minimal fiscal support, its operation is expected to finally terminate following December, 2013. Jeff has been keen for some time to capture a large flare with the maximum possible spectral coverage. He has therefore submitted the attached for our consideration. We have been seeking to partially achieve his goal in the EIS team programme but so far have only obtained limited coverage of small flares - hence this broader request which will have enhnaced value given the availability of IRIS.