at harmonics of the cyclotron frequency gives a direct conversion between observing frequency and field strength. With high-resolution imaging at a large number of frequencies, the FASR will directly obtain iso-gauss contours at the corresponding field strength in every active region on the disk simultaneously. In lower-field regions such as quiet Sun network, the FASR will exploit the magnetic sensitivity of circularly polarized free-free emission to yield line-of-sight magnetic field strength. Both techniques measure the magnetic field well above the photospheric height accessible to optical magnetographs.

  1. True Coronal Temperatures: Radio emission allows direct measurement of the electron temperature, which is a true temperature that does not depend on abundances or atomic physics. Wherever the radio emission is optically thick (which occurs somewhere within the broad frequency range of FASR for virtually every solar feature), the radio brightness is strictly proportional to the electron temperature. For regions dominated by gyroresonance emission (B > 100 G), the temperature measurement refers to a very specific layer just 100 km wide which changes with the observing frequency. FASR will continuously map true coronal/chromospheric temperature over the entire solar disk and with exquisite height precision in active regions.

  2. Origins of Solar Activity: Radio emission is far more sensitive to non-thermal, high-energy electrons than is X-ray emission. The FASR will obtain diagnostics of electron energy distributions, with high spatial resolution, continuously over the entire visible hemisphere of the Sun, with activity ranging in size from tiny microflares to the largest solar events. The wide frequency range and high dynamic range will allow simultaneous, perfectly cospatial imaging of both the thermal and nonthermal counterparts of solar activity, including the initiation and propagation of CMEs, filament eruptions and flares. Comparison with pre-event coronal magnetograms and temperature maps from the FASR can help to reveal the root causes of the Sun's activity.

KEY ARRAY CHARACTERISTICS

Size of elements: 2 m

Number of elements: ~ 40

Maximum baseline: 3 km

Minimum baseline: 3 m

Sky coverage: all-sky within 3 degrees of horizon

Large elements for calibration: 1 to 3 large (25-meter-class) antennas allow determination of absolute flux and position using cosmic sources, to arc-sec accuracy

KEY RECEIVER CHARACTERISTICS

Time resolution: 1 s

Frequency range: 300-26,000 MHz

IF bandwidth: 500 MHz



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