Sighting of a possible beam or tether directly connected from the ground to an aircraft at an altitude of 2,500 ft.Looking to the South from my 2nd story kitchen window, what I first observed was what appeared to be a blue/purple beam, which was wavy in shape, but completely linear in direction. This beam had the appearance of a thin streak of lightning, yet was relatively dim. It appeared to be fluorescent in nature, as opposed to lighted from any external light source. The beam was very clearly connected to the ground, approximately 1/4-mile south from my location. Upon first sighting the beam, it was angled away from me at approximately 60 degrees from the horizon, facing Southeast. Following the beam upwards, it grew dimmer with distance, becoming invisible to the eye at approximately 200-300 meters. Upon following the beams upward trajectory, I spotted an aircraft flying at approximately 2,500 ft. in a North to South trajectory, with seemingly normal exterior lights: 2 white strobe lights, with 1 steady dim red light between the 2 white strobes. The strobes were blinking together, at an interval of 2 quick strobes in rapid succession separated by 3/4 (.75) second between bursts. The strange beam appeared to be literally connected to this aircraft, although at that distance I could not confirm this due to the beam becoming too dim at that altitude. The reason I say that the beam appeared connected to the craft is this; as the aircraft passed overhead from South to North, the angle of the beam changed precisely with this movement as though it were tracking the aircraft or being emitted from the aircraft to a fixed ground location. I lost sight of the aircraft several times, but needed only to follow the path of this beam upwards to relocate the aircraft's position. The angle of the beam changed from and angle of 60 degrees facing South East, to 90 degrees straight up, to an angle of 45 degrees facing North, precisely in unison with the aircraft as though it were a tether of some sort, attached to the aircraft and fixed to the ground. The aircraft proceeded to fly in its linear trajectory to the north, until at s! uch a di stance as to be no longer visible. The beam remained pointing to the north in the direction of the aircraft's last visible position, for several minutes preceding the aircraft's departure. I observed the beam as well as the aircraft through my binoculars. At this higher magnification, the beam appeared unsolid and quite wide. The structure of the beam was wavy, similar to the structure of lightening, although its path was ultimately perfectly linear. The beam maintained a constant luminosity, and did not appear to be changing shape, despite its wavy, electricity-like appearance. The width of the beam was comparable to a toothpick held at arm's length, and was blue/purple in hue. The closest comparison I can think of to describe this beam would be a semi-transparent fluorescent tube. It was also comparable to a thin, focused beam shining through haze, although it was a clear night. I have ruled out the possibility of some sort of physical tether, i.e. kite string, for the following reasons: 1) The apparent size was far too thick - a tether seen from even as close as 1/4 mile away would be nearly invisibly thin, were it any less than 6 inches in thickness. 2) The linearity of the line was absolutely perfect - it was not sagging earthward as would be expected with any sort of tether, even under extreme tension. Yet it truly appeared to be anchored to the aircraft above, as well as the ground below. After observing the beam and aircraft for 1 minute and it became apparent that their motions were somehow unified, I awoke my wife from bed so that she could verify what I was seeing. She was easily able to see the beam, which she said appeared to her like a high-flying jet plane's vapor trail, but aiming directly into the ground at a very close distance. After the aircraft had left, and the beam had ceased movement but was still visible, I decided to leave my home to try and locate the point where it contacted the ground. As soon as I was on ground level, my vertical line of sight was too narrow and the su! rroundin g lights were too bright so that I could no longer see the beam. I quickly returned to my second floor window to verify it was still visible. It was, so I again left my home and drove in my car to approximately directly below and a bit closer to where I suspected the beam to be. The drive was approximately 1 minute. I searched the sky for an additional minute, and then returned home. I was away from home for no longer than 4 minutes. Upon returning home, the beam was no longer visible. In hindsight, I should have remained at home and kept the beam in sight. But my curiosity was too great, and the beam disappeared sometime during my 4-minute search away from home. The total duration of this sighting was approximately 8 minutes, from the moment I first observed the beam, to the moment I left my home to search for its source. At no point was any sound audible. I am an amateur astronomer and aviation enthusiast, so I am constantly observing the sky and local aircraft with a telescope and binoculars, but have never witnessed anything abnormal until now. My father is an international pilot, and we have discussed the many highly strange natural phenomena that he observes regularly during his flight paths over the Atlantic and Pacific Oceans and the Arctic. My understanding is that this phenomenon is completely unique, so I am extremely curious to learn if any other similar observances have occurred elsewhere.