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Solar Transients and Space Weather (STSW)

Science Highlights

From De Pontieu & McIntosh 2010 (Submitted to Science) Combining observations of the Hinode and Solar Dynamics Observatory (SDO) spacecraft we have identified, and started to explore, discrete coronal heating events - for the first time tracking plasma heating from the low chromosphere (~10,000 K) into the extended corona (>2,000,000 K). These episodic heating events appear to be rooted in activity of the smallest (visible) scales of solar magnetism observed by Hinode/SP and have been unambiguously shown to manifest as very fine (~100km in diameter), rapidly traveling (~100km/s), and short-lived (10-100s) "Type-II" spicules, so-called to distinguish them from their classical siblings (≤1Mm across, 20-40 km/s, several minutes in duration). Tracking these rapid events through images of the Sun's chromosphere provided by Hinode has revealed a one-to-one relationship with material that is considerably hotter moving upwards at the same apparent speed into the corona (with SDO) across many temperatures, often exceeding 2 million Kelvin.

Relevance: These observations (see figure below) have provided a challenge to existing models of coronal heating by demonstrating that the majority of coronal temperature mass is dynamically forced out of the chromosphere pre-heated. The observed process provides strong constraint on the relentless cycling of mass between the Sun's surface and outer solar atmosphere. Such knowledge will (in-turn) permit the modeling of ultraviolet and extreme-ultraviolet radiation formation in the solar atmosphere that impinges on the Earth's outer atmosphere.

Future: Observational investigations will attempt to isolate the relationship between magnetic field emergence, strength, geometry, and post-emergence evolution as likely "trigger" mechanisms for the launch and heating of the spicule material. It is imperative that the highest quality simulations of the middle atmospheric region are developed in tandem to place the observations in a quantitative context.