TRACE Science Objectives

TRACE enables solar physicists to study the connections between fine-scale magnetic fields and the associated plasma structures on the Sun in a quantitative way by observing the photosphere, the transition region, and the corona. With TRACE, these temperature domains are observed nearly simultaneously (with as little delay as only a second between different wavelengths), with a spatial resolution of one second of arc.

This is accomplished by obtaining precisely coaligned image sequences of photosphere, transition region, and corona, with high spatial resolution and uninterrupted viewing of the Sun for up to eight months.

TRACE Mission

	TRACE was launched on a Pegasus launch vehicle from Vandenberg Air Force Base in April 1998. The launch was scheduled to allow joint observations with SOHO during the rising phase of the solar cycle to sunspot maximum. No transition region or coronal imager has witnessed the onset and rise of a solar cycle.
Pegasus in flight

The two satellites provide complementary observations: TRACE produces the high spatial and temporal resolution images, while SoHO yields images and spectral data out to 30 solar radii at much lower spatial and temporal resolution. Jointly they provide the opportunity to obtain simultaneous digital measurements of all the temperature regimes of the solar atmosphere, in both high-resolution imaging and spectroscopy.

With these data, we expect to shatter the current ignorance of coronal heating and impulsive MHD phenomena, with benefits not only to solar physics, but also to studies ranging from stellar activity to the MHD of accretion disks. The magnetograms produced by MDI on SoHO provide a complete record of the eruption and distribution of photosphere magnetic fields which will be invaluable for understanding TRACE observations of coronal hole formation and coronal mass ejections. Both of these phenomena have profound effects on our space environment and the Earth`s magnetic field.

TRACE is the first U.S. solar research satellite since the Solar Maximum Mission.

Coordination with SOHO provides an unprecedented opportunity to follow the emergence of magnetic flux from the base of the convection zone deep inside the Sun, through the photosphere, chromosphere and transitional region, to the low-beta outer corona, while observing the effects of this emergence, such as coronal mass ejections, with high spatial and temporal resolution.

The transition from the photosphere, where magnetic fields and plasma are in rough equipartition, to the corona, where magnetic fields dominate, is extremely difficult to model and, until recently, to observe at high temporal and spatial resolution. Many of the physical problems that arise here, such as plasma confinement, reconnection, wave propagation, and plasma heating arise throughout space physics and astrophysics. The detailed study of these processed in the solar outer atmosphere is invaluable to astrophysics in general, and stellar studies in particular.