ACE Magnetic Field Detector KP Data Caveat

The Magnetic Field Experiment (MAG) consists of twin vector fluxgate magnetometers controlled by a common CPU. The sensors are mounted on booms extending 4.19 meters from the center of the spacecraft at opposite sides along the +/-Y axes of the spacecraft. The instrument returns 6 vector measurements each second, divided between the two sensors, with onboard snapshot and FFT buffers to enhance the high-frequency resolution.

Browse data for the MAG instrument consists of 16-second, major-frame averages of the measured magnetic field with subsequent analysis yielding 5-minute, 1-hour and 1-day averages consistent with Browse data from other ACE instruments. Instrument offsets, including spacecraft fields, are derived from past weeks of data and necessarily lag behind the most accurate values computed for use in Level-2 analyses. Users of Browse data should be aware that spurious AC signals, such as possible spacecraft or instrument noise, are not detected and are not removed from the Browse analysis. Depending on the accuracy and stability of offsets applied in the above manner, spacecraft spin tones may be evident in the data. MAG data is not guaranteed during spacecraft maneuvers and spacecraft nutation is likely to contribute directional errors following maneuvers.

MAG Browse data is not validated by the experimenters and should not be used except for preliminary examination prior to detailed studies.

ACE Electron, Proton, and Alpha Monitor KP Data Caveat

Note: The Electron, Proton, and Alpha Monitor (EPAM) is designed to make measurements of ions and electrons over a broad range of energy and intensity. Through five separate solid-state detector telescopes oriented so as to provide nearly full coverage of the unit-sphere, EPAM can uniquely distinguish ions (E > 47 keV) and electrons (E > 38 keV) providing the context for the measurements of the high sensitivity instruments on ACE.

The browse parameters contain spin averaged data coming from two of the five telescopes. The full resolution and angular data is available from the Johns Hopkins University Applied Physics Laboratory. EPAM is also part of the real-time Solar Wind (RTSW) system developed by NASA and NOAA. The instrument provides 24 hour coverage of the space weather environment as measured by ACE. For additional information contact Dennis Haggerty (Dennis.Haggerty@jhuapl.edu) or Rob Gold (Robert.Gold@jhuapl.edu).

This 761-1220 keV ion channel is on a telescope referred to as LEFS60 (Low Energy Foil Spectrometer). An aluminized Parylene foil is used to absorb ions with energies below 350 keV while allowing ions above 350 keV to pass through to the solid-state detector. The telescope is mounted at 60 degrees to the spacecraft spin axis. The geometrical factor for this channel is 0.397 (cm2.sr).

These channels come from EPAM's Low-Energy Magnetic Spectrometer which is oriented at 30 degrees from the spacecraft spin axis and is known as the LEMS30 telescope. The LEMS30 telescope contains a rare-earth magnet in front of the detector and sweeps out electrons with energy below about 500 keV. The flux conversions for these browse channels use a geometrical factor of 0.428 (cm2 sr).

These deflected electron channels are a byproduct of EPAM's Low-Energy Magnetic Spectrometer which is oriented at 30 degrees from the spacecraft spin axis and is known as LEMS30. The rare-earth magnet in front of the LEMS30 detector deflects electrons away from the ion detector and samples them in a separate detector known as the B detector. Only deflected electrons can reach the B detector so it is not susceptible to ion contamination The geometrical factor for these channels is 0.14 (cm2 sr).

EPAM Home Page.

EPAM Browse data is not validated by the experimenters and should not be used except for preliminary examination prior to detailed studies.

ACE Solar Isotope Spectrometer KP Data Caveat

SIS Browse data is not validated by the experimenters and should not be used except for preliminary examination prior to detailed studies.

Note: During periods of high solar activity, the livetime for these browse parameters may not be calculated correctly, resulting in incorrect flux values.
Two noisy matrix strip in the instrument were turned off on 2000-318. These strips were causing the livetime for these browse parameters to be calculated incorrectly. This is the cause of the apparent large drop in flux on 2000-318.

Integral flux of high-energy solar protons from the T4 and T67 counting rates of the Solar Isotope Spectrometer (SIS). These browse parameters are designed to emulate the SIS proton rates contained in ACE Real Time Solar Wind Data from NOAA.

During solar quiet times, these fluxes are contaminated by background from particles entering from the sides of the instrument.

This browse parameter is derived from the counting rate of energetic CNO nuclei that stop in the two solid state detector telescopes that make up the Solar Isotope Spectrometer (SIS). Included are events with nuclear charge 3 <= Z <= 9 that trigger detectors M1 and M2, and then stop before triggering detector D1. The 3 <= Z <= 9 element range is always dominated by C, N, and O nuclei, independent of the source of the particles being observed.

During solar minimum (e.g., 1992 to 1998), on days when the Sun is quiet, the 7 to 10 MeV/nuc energy interval is dominated by anomalous cosmic ray (ACR) nitrogen and oxygen, with a small contribution (< 10%) from galactic cosmic rays (GCRs). Anomalous cosmic rays originate from interstellar neutral particles that are swept into the heliosphere, ionized, picked up by the solar wind and carried to the solar wind termination shock, where they are accelerated to energies of ~1 to ~50 MeV/nuc. The flux of these nuclei sometimes varies by as much as a factor of ~2 over the 27 day solar rotation period in response to interplanetary conditions. The ~40 cm2sr geometry factor of SIS allows these variations to be seen clearly. As we move toward solar maximum conditions in 1999 and beyond, the flux of ACRs is expected to decrease by a factor of ~100 or more, as it becomes more difficult for low energy cosmic rays to enter the inner heliosphere.

During large solar energetic particle (SEP) events, the intensity of low energy nuclei in interplanetary space can increase by factor of 10 to 1000 or more, and for days at a time, this energy interval can be dominated by solar energetic particles with C:N:O ~ 0.4:0.15:1. An example of such an event is seen in early November of 1997 (~Day 310). The quiet time intensity measured by this browse parameter should vary from ~10-8 per cm2sr.sec.MeV/nuc at solar maximum to ~10-6 per cm2sr.sec.MeV/nuc at solar minimum. During large solar particles events it could be as high as ~1 per cm2sr.sec.MeV/nuc.

Qualifying Remarks:

Note that the energy intervals for the most abundant elements C, N, and O all differ somewhat from the nominal values of 7 to 10 MeV/nuc.

This browse parameter is derived from the counting rate of energetic CNO nuclei that stop in the two solid state detector telescopes that make up the Solar Isotope Spectrometer (SIS). Included are events with nuclear charge 3 <= Z <= 9 that trigger detectors M1 and M2 then stop in either D1 or D2. This element range 3 <= Z <= 9 is always dominated by C, N, and O nuclei, independent of the source of the particles being observed.

This browse parameter responds mainly to anomalous cosmic rays during solar-minimum quiet times, to galactic cosmic rays during solar maximum quiet times, and to solar particles during large solar energetic particle events (see discussion for the 7 to 10 MeV/nuc CNO browse parameter). The quiet time flux should vary from a few x 10-8 per cm2sr.sec.MeV/nuc at solar maximum to ~10-5 per cm2sr.sec.MeV/nuc at solar minimum. During large solar particles events it could be as high as ~0.1 per cm2sr.sec.MeV/nuc.

Qualifying Remarks:

Note that the energy intervals for the dominant elements C, N, and O all differ somewhat from the nominal values of 10 to 15 MeV/nuc, and that the relative abundance of the contributing elements depend on the source of the particles, as noted above and in the description of other SIS browse parameters.

SIS measurements of the intensity of ~9 to ~21 MeV/nuc Z>=10 nuclei are derived from the counting rate of energetic nuclei that stop in the two solid state detector telescopes that make up the Solar Isotope Spectrometer (SIS). Included are events with nuclear charge 10<=Z<=28 (Ne to Ni) that trigger detectors M1 and M2 and then stop in either M2, D1, or D2. The most abundant elements in the element range 10<=Z<=28 are Ne (Z=10), Mg (Z=12), Si (Z=14) and Fe (Z=26).

During solar quiet times this browse parameter responds mainly to galactic cosmic rays, with an admixture of anomalous cosmic ray Ne (see also discussion of 7 to 10 MeV/nuc CNO browse parameter from SIS). During large solar particle events the intensity can be orders of magnitude greater for periods of days. The quiet time intensity should vary from ~10-8 per cm2sr.sec.MeV/nuc at solar maximum to a few times 10-7 per cm2sr.sec.MeV/nuc at solar minimum. During large solar particle events the intensity could rise to >10-2 per cm2sr.sec.MeV/nuc.

Qualifying Remarks:

Note that the quoted energy interval of ~9 to 21 MeV/nuc is strictly valid only for Si. For Ne the corresponding interval is ~8 to ~17 MeV/nuc, while for Fe it is ~12 to ~26 MeV/nuc.

For more information on SIS, see The CRIS/SIS Home Page.

SWEPAM KP Data Caveat

SWEPAM Browse data is not validated by the experimenters and should not be used except for preliminary examination prior to detailed studies.

Proton density (np) -
is the proton number density in units of cm-3, as calculated by integrating the ion distribution function.

Proton speed (vp) -
is the solar wind proton speed, or more generally just the solar wind (bulk) speed. It is also obtained by integrating the ion (proton) distribution function.

Helium ratio (nHe/np) -
is the ratio of the number density of helium++ ions to the number density of protons.

The radial component of the proton temperature (Tp,rr) -
is the (1,1) component of the temperature tensor, along the radial direction. Again, it is obtained by integration of the ion (proton) distribution function.

For more information contact Dave McComas (dmccomas@swri.edu) or visit the SWEPAM website at http://swepam.lanl.gov/.