Decadal and annual variations in meteoric flux from Ulysses, Wind, and
SOFIE observations
Abstract
Our solar system is filled with meteoric particles, or cosmic dust,
which is either interplanetary or interstellar in origin. Interstellar
dust (ISD) enters the heliosphere due to the relative motion of the sun
and the interstellar flow. Interplanetary dust (IPD) comes primarily
from asteroid collisions or comet sublimation, and comprises the bulk of
material entering Earth’s atmosphere. This study examines variations in
ISD and the IPD flux at Earth using observations from three different
satellite techniques. First are size-resolved in situ meteoroid
detections by the Ulysses spacecraft, and second are in situ indirect
dust observations by Wind. Third are measurements of meteoric smoke in
the mesosphere by the Solar Occultation For Ice Experiment (SOFIE). Wind
observations are sorted into the interstellar and interplanetary
components. Wind ISD show the anticipated correlation to the 22-yr.
solar magnetic cycle, and are consistent with model predictions of ISD.
Because Wind does not discriminate particle size, the IPD measurements
were interpreted using meteoric mass distributions from Ulysses
observations and from different models. Wind observations during
2007-2020 indicate a total meteoric influx at Earth of 22 metric tons
per day (t d-1), in reasonable agreement with
long-term averages from SOFIE (25 t d-1) and Ulysses
(32 t d-1). The SOFIE and Wind influx time series both
show an unexpected correlation to the 22-yr. solar cycle. This
relationship could be an artifact, or may indicate that IPD responds to
changes in the solar magnetic field.