LWS TR&T Focus Teams:
Jets in the Solar Atmosphere and their Effects in the Heliosphere
Team Leader: Ed DeLuca (Harvard-Smithsonian CfA)
Target Description: One of the most striking features of the solar atmosphere is that it exhibits jetting activity at all size scales and at all temperature regimes; in fact, the upper chromosphere may well be nothing more than a collection of spicules. Consequently, developing predictive models for the coupling of the chromosphere to corona requires a comprehensive understanding of the origins and dynamics of jets. Although ubiquitous in the chromosphere and transition region, often identified as ³explosive events,² jets are also commonly seen in X-ray observations, especially in coronal hole regions where they may be playing an important role in the origin and properties of the solar wind. SOHO and STEREO have revealed that polar jets can extend out to beyond a solar radius and are related to plumes, which are ubiquitous in coronal holes. Hence, a deep understanding of jets may also be critical for modeling the coupling of the corona to the wind. Jets have long been proposed as a possible mechanism by which both coronal loops and prominences gain their mass. Furthermore, the recent results from Hinode and other spectroscopic instruments indicate that jets may be playing a central role in coronal heating. In addition, they have also been suggested to be sites of particle acceleration. Physical models for their origin have been proposed and range from magnetic reconnection to wave pressure driven mass lifting, but the underlying mechanisms for jet acceleration are still widely debated.
The problem of solar jets is now ripe for a focused team attack. We now have unprecedented new data from SDO and STEREO, which allow us to study the complete thermal evolution of jet material from chromospheric to hot coronal temperatures and spatial evolution from the chromosphere out to the wind. One of the major mysteries of the recently discovered type II spicules by Hinode is that much more mass is observed to accelerate upward than to fall back down. The most likely explanation is that the mass heats up to temperatures outside the Hinode temperature range. SDO, with its extensive temperature coverage and high time resolution, will be able to resolve the evolution of the jet material and, thereby, help determine the role of jets in coronal heating and in solar wind acceleration.
Goals and Measures of Success: The goal of this FST is to advance our understanding of the origins, structure, and dynamics of chromospheric and coronal jets; their extension into the solar wind; and their role in accelerating charged particles. This Topic is focused on jets rather than on major dynamic events such as eruptive flares and CMEs; however, comparative studies of possible relationships between the jet phenomena and CMEs/eruptive flares would be appropriate to this Topic. The prime measure of success for this work would be the development of accurate models for the UV X-ray emission from jets, their contribution to the mass and energy flux of both the closed field and the open field corona and wind, and for their role in particle acceleration. Measures of success are the following: Development of improved models of E and F region plasma instabilities and turbulence; Establishment of the connection (if any) between E and F region irregularities; Identification of the causes of day-to-day variability of irregularities; Understanding of the connection between large-scale ionospheric processes and the development of electron density irregularities (e.g., equatorial spread F); and € Development of a predictive capability for irregularity onset and evolution.
Types of Investigations: