Main Objective:
We propose to do a detailed search for and investigation of any chromospheric enhancement or dynamics associated with the small-scale, ubiquitous highvelocity events seen in the quiet photosphere.
Scientific Justification:
The discovery in Sunrise/IMaX data high-velocity events in the quiet Sun (Borrero et al. 2010) revealed the unexpected presence of supersonic motions in the quiet solar photosphere. However, the limited spectral sampling of the IMaX instrument precluded detailed study of these events. Follow-on studies (Martínez Pillet et al. 2011, Quintero Noda et al. 2014) used the extended wavelength coverage of the Hinode/SOT instruments to fully characterize the photospheric dynamics of this phenomenon. Martínez Pillet et al. (2011) suggested that the jets arise from reconnection of emerging fields with pre-existing fields in the photosphere. Using data from the spectro-polarimeter (SP) of Hinode/SOT, Quintero Noda et al. (2014) examined red-shifted magnetic signals located within the intergranular lanes, along with Doppler imaging in the upper photospheric MgI b2 and imaging in the chromospheric Ca II HÊline from Hinode/SOT, in an effort to identify a chromoshperic counterpart to these particular downwardflowing photospheric jets. They found that the majority of their red-shifted jets were associated with down flows seen in Mg I b2 line and bright points in the Ca II broadband images.
The question still remains as to whether these photospheric events can be connected with some dynamic or heating events in higher layers, and thus possibly a significant contributor to chromospheric heating and dynamics in the quiet Sun. For example, do the photospheric jets have a connection to the Rapid Blueshifted Excursions (RBEs, Langangen et al. 2008) now known to be associated with type II spicules? The previous studies of these photospheric jets were unable to determine a precise association with a chromospheric counterpart owing the broad spectral bandwidth of the Ca II imaging of Hinode/SOT, and also to the lack of spectroscopic data of the chromosphere. This limitation may now be addressed effectively with co-spatial, co-temporal spectroscopy using both Hinode/SOT SP and IRIS.
We propose to use co-spatial, co-temporal spectrographic observations using the Hinode/SOT spectro-polarimeter and IRIS spectrograph to search for chromospheric manifestations of the photospheric jets. Such observations should be able to identify the connection, if it exists, and further to provide quantitative information on the dynamics and energetics of the associated phenomena. For this purpose we propose to carry out time series of short maps using both SP and IRIS. The Hinode/SOT SP will make repeated gvery fast maph observations of quiet regions near the center of the disk, with a cadence of about one minute in order to temporally resolve the photospheric jets (lasting of order 3-4 minutes).
From prior studies of these events, it is known that they occupy a few spatial resolution elements of the SP, so the compromise of spatial resolution rendered by the very fast map program should not be detrimental to the study. Further, with IRIS we propose to carry out spectrographic measurements of the Mg II hor k-line, and if possible also lines forming at higher temperatures, co-aligned and co-temporal with the Hinode/SOT SP observations, and covering an area comparable in extent to the SP maps in order to compensate for pointing offsets between the two spacecraft. |
|