3.6 Flying Out of the Solar System
193
the Sun slow down and turn inward, and the magnetic field of the solar system
is doubled in strength as interstellar space appears to be applying pressure. The
energetic particles originating from the solar system decline by nearly half while the
detection of high-energy electrons from outside increases 100 folds.
Since May 2012, the Voyager-1 had detected that the energetic particle accounts
with an energy spectrum of above 70 MeV were increasing dramatically. In general,
it is considered that the energetic particles are generated by the cosmic rays from the
distant supernovae outside the solar system. In June 2012, the NASA announced that
the Voyager-1 was detecting changes in the environment that were suspected to correlate with arrival at the heliopause. Based on the detection data from the Voyager-1, it
had been reported that the charged particles from interstellar space increased significantly. The charged particles from the Sun can not be detected normally as they are
deflected by the solar wind within the heliosphere. On August 25, 2012, particularly
the Voyager-1 detected that the high-energy particles from interstellar space increased
steeply while the low-energy particles from the solar wind decreased suddenly. In
September 2012, the Voyager-1 was traveling at a velocity of 17.0 km/s relative to
the Sun, with the distance of 121 AU away from the Sun. A space scientist at Johns
Hopkins University and principal investigator for the Low-Energy Charged Particle
instruments onboard of the Voyager spacecrafts, Edmond C. Roelof declared: “Most
scientists involved with Voyager-1 would agree that these two criteria have been sufficiently satisfied”. However, the last criterion that the magnetic field direction was
significantly changed from the Sun to the interstellar space had not been observed.
From the actual measurement, the change of magnetic field direction was only two
degrees. In other words, the Voyager-1 was traveling at the physical boundary of the
solar system and would enter interstellar space at any time. On December 3, 2012,
Ed Stone said: “Voyager has discovered that a new region of the Heliosphere that we
had not realized was there. We are still inside, apparently. But the magnetic field now
is connected to the outside. So it is like a highway letting particles in and out”. In this
region, the magnetic field was 10 times more intense than the Voyager-1 encountered
the termination shock. It was expected to be the last barrier before the Voyager-1
exited the solar system completely and entered interstellar space.
Until September 2013, it was being debating whether the new region where the
Voyager-1 was traveling was interstellar space or an unknown region of the solar
system. Finally, the NASA officially confirmed that the Voyager-1 had reached
the interstellar space in August 25, 2012. The final conclusion from the NASA
made most of space scientists had abandoned the assumption that the direction of
magnetic field must be changed when passing through the heliopause, and improved
the heliopause’s model. A key evidence to persuade the scientists that the Voyager1 had crossed through the heliopause was an indirect measurement of an 80 folds
increase in electron density. It was originated from a solar outburst that had occurred
in March 2012, triggering the frequency of plasma oscillations in April 2013, and
thus the electron density could be measured indirectly, which was generally expected
to be two orders of magnitude higher outside the heliopause than within. Actually,
additional data was also provided with the weaker sets of oscillations measured in
October and November 2012. As early as 1980, the plasma spectrometer onboard
193
the Sun slow down and turn inward, and the magnetic field of the solar system
is doubled in strength as interstellar space appears to be applying pressure. The
energetic particles originating from the solar system decline by nearly half while the
detection of high-energy electrons from outside increases 100 folds.
Since May 2012, the Voyager-1 had detected that the energetic particle accounts
with an energy spectrum of above 70 MeV were increasing dramatically. In general,
it is considered that the energetic particles are generated by the cosmic rays from the
distant supernovae outside the solar system. In June 2012, the NASA announced that
the Voyager-1 was detecting changes in the environment that were suspected to correlate with arrival at the heliopause. Based on the detection data from the Voyager-1, it
had been reported that the charged particles from interstellar space increased significantly. The charged particles from the Sun can not be detected normally as they are
deflected by the solar wind within the heliosphere. On August 25, 2012, particularly
the Voyager-1 detected that the high-energy particles from interstellar space increased
steeply while the low-energy particles from the solar wind decreased suddenly. In
September 2012, the Voyager-1 was traveling at a velocity of 17.0 km/s relative to
the Sun, with the distance of 121 AU away from the Sun. A space scientist at Johns
Hopkins University and principal investigator for the Low-Energy Charged Particle
instruments onboard of the Voyager spacecrafts, Edmond C. Roelof declared: “Most
scientists involved with Voyager-1 would agree that these two criteria have been sufficiently satisfied”. However, the last criterion that the magnetic field direction was
significantly changed from the Sun to the interstellar space had not been observed.
From the actual measurement, the change of magnetic field direction was only two
degrees. In other words, the Voyager-1 was traveling at the physical boundary of the
solar system and would enter interstellar space at any time. On December 3, 2012,
Ed Stone said: “Voyager has discovered that a new region of the Heliosphere that we
had not realized was there. We are still inside, apparently. But the magnetic field now
is connected to the outside. So it is like a highway letting particles in and out”. In this
region, the magnetic field was 10 times more intense than the Voyager-1 encountered
the termination shock. It was expected to be the last barrier before the Voyager-1
exited the solar system completely and entered interstellar space.
Until September 2013, it was being debating whether the new region where the
Voyager-1 was traveling was interstellar space or an unknown region of the solar
system. Finally, the NASA officially confirmed that the Voyager-1 had reached
the interstellar space in August 25, 2012. The final conclusion from the NASA
made most of space scientists had abandoned the assumption that the direction of
magnetic field must be changed when passing through the heliopause, and improved
the heliopause’s model. A key evidence to persuade the scientists that the Voyager1 had crossed through the heliopause was an indirect measurement of an 80 folds
increase in electron density. It was originated from a solar outburst that had occurred
in March 2012, triggering the frequency of plasma oscillations in April 2013, and
thus the electron density could be measured indirectly, which was generally expected
to be two orders of magnitude higher outside the heliopause than within. Actually,
additional data was also provided with the weaker sets of oscillations measured in
October and November 2012. As early as 1980, the plasma spectrometer onboard